diff --git a/examples/data/rag_travel.txt b/examples/data/rag_travel.txt
new file mode 100644
index 000000000..1c738c54a
--- /dev/null
+++ b/examples/data/rag_travel.txt
@@ -0,0 +1 @@
+Bojan likes traveling.
\ No newline at end of file
diff --git a/examples/data/rag.txt b/examples/data/rag_writer.txt
similarity index 100%
rename from examples/data/rag.txt
rename to examples/data/rag_writer.txt
diff --git a/examples/rag_pipeline.py b/examples/rag_pipeline.py
index c90b160f3..ba8287f4b 100644
--- a/examples/rag_pipeline.py
+++ b/examples/rag_pipeline.py
@@ -9,7 +9,7 @@ from metagpt.rag.schema import (
     LLMRankerConfig,
 )
 
-DOC_PATH = EXAMPLE_PATH / "data/rag.txt"
+DOC_PATH = EXAMPLE_PATH / "data/rag_writer.txt"
 QUESTION = "What are key qualities to be a good writer?"
 
 
@@ -26,7 +26,16 @@ def print_result(result, state="Retrieve"):
     print(result)
 
 
-async def rag_pipeline():
+def build_engine(input_files: list[str]):
+    engine = SimpleEngine.from_docs(
+        input_files=input_files,
+        retriever_configs=[FAISSRetrieverConfig(), BM25RetrieverConfig()],
+        ranker_configs=[LLMRankerConfig()],
+    )
+    return engine
+
+
+async def rag_pipeline(engine: SimpleEngine, question=QUESTION):
     """This example run rag pipeline, use faiss&bm25 retriever and llm ranker, will print something like:
 
     Retrieve Result:
@@ -37,22 +46,48 @@ async def rag_pipeline():
     Query Result:
     Passion, adaptability, open-mindedness, creativity, discipline, and empathy are key qualities to be a good writer.
     """
-    engine = SimpleEngine.from_docs(
-        input_files=[DOC_PATH],
-        retriever_configs=[FAISSRetrieverConfig(), BM25RetrieverConfig()],
-        ranker_configs=[LLMRankerConfig()],
-    )
-
-    nodes = await engine.aretrieve(QUESTION)
+    nodes = await engine.aretrieve(question)
     print_result(nodes, state="Retrieve")
 
-    answer = await engine.aquery(QUESTION)
+    answer = await engine.aquery(question)
     print_result(answer, state="Query")
 
 
+async def rag_add_docs(engine: SimpleEngine):
+    """This example show how to add docs, before add docs llm anwser I don't know, after add docs llm give the correct answer, will print something like:
+
+    [Before add docs]
+    --------------------------------------------------
+    Retrieve Result:
+    --------------------------------------------------
+    Query Result:
+    I don't know.
+
+    [After add docs]
+    --------------------------------------------------
+    Retrieve Result:
+    0. Bojan like..., 10.0
+    --------------------------------------------------
+    Query Result:
+    Bojan likes traveling.
+    """
+    travel_question = "What does Bojan like? If you not sure, just answer i don't know"
+    travel_filepath = EXAMPLE_PATH / "data/rag_travel.txt"
+
+    print("[Before add docs]")
+    await rag_pipeline(engine, question=travel_question)
+
+    print("\n[After add docs]")
+    engine.add_docs([travel_filepath])
+    await rag_pipeline(engine, question=travel_question)
+
+
 async def main():
     """RAG pipeline"""
-    await rag_pipeline()
+    engine = build_engine([DOC_PATH])
+    await rag_pipeline(engine)
+    print("#" * 100)
+    await rag_add_docs(engine)
 
 
 if __name__ == "__main__":
diff --git a/metagpt/rag/engines/__init__.py b/metagpt/rag/engines/__init__.py
index 7b4e37e88..4e862b908 100644
--- a/metagpt/rag/engines/__init__.py
+++ b/metagpt/rag/engines/__init__.py
@@ -1,3 +1,6 @@
-from metagpt.rag.engines.simple import SimpleEngine
+"""Engines init"""
 
 __all__ = ["SimpleEngine"]
+
+
+from metagpt.rag.engines.simple import SimpleEngine
diff --git a/metagpt/rag/engines/simple.py b/metagpt/rag/engines/simple.py
index 3f6f15aad..e136b4092 100644
--- a/metagpt/rag/engines/simple.py
+++ b/metagpt/rag/engines/simple.py
@@ -1,6 +1,7 @@
 """Simple Engine."""
 
-from llama_index import ServiceContext, SimpleDirectoryReader
+
+from llama_index import ServiceContext, SimpleDirectoryReader, VectorStoreIndex
 from llama_index.embeddings.base import BaseEmbedding
 from llama_index.llms.llm import LLM
 from llama_index.query_engine import RetrieverQueryEngine
@@ -9,26 +10,23 @@ from llama_index.schema import NodeWithScore, QueryBundle, QueryType
 from metagpt.rag.llm import get_default_llm
 from metagpt.rag.rankers import get_rankers
 from metagpt.rag.retrievers import get_retriever
-from metagpt.rag.schema import RankerConfig, RetrieverConfig
+from metagpt.rag.retrievers.base import RAGRetriever
+from metagpt.rag.schema import RankerConfigType, RetrieverConfigType
 from metagpt.utils.embedding import get_embedding
 
 
 class SimpleEngine(RetrieverQueryEngine):
-    """
-    SimpleEngine is a search engine that uses a vector index for retrieving documents.
-    """
-
     @classmethod
     def from_docs(
         cls,
         input_dir: str = None,
-        input_files: list = None,
+        input_files: list[str] = None,
         llm: LLM = None,
         embed_model: BaseEmbedding = None,
         chunk_size: int = None,
         chunk_overlap: int = None,
-        retriever_configs: list[RetrieverConfig] = None,
-        ranker_configs: list[RankerConfig] = None,
+        retriever_configs: list[RetrieverConfigType] = None,
+        ranker_configs: list[RankerConfigType] = None,
     ) -> "SimpleEngine":
         """This engine is designed to be simple and straightforward
 
@@ -44,8 +42,8 @@ class SimpleEngine(RetrieverQueryEngine):
             chunk_size=chunk_size,
             chunk_overlap=chunk_overlap,
         )
-        nodes = service_context.node_parser.get_nodes_from_documents(documents)
-        retriever = get_retriever(nodes, configs=retriever_configs, service_context=service_context)
+        index = VectorStoreIndex.from_documents(documents, service_context=service_context)
+        retriever = get_retriever(index, configs=retriever_configs)
         rankers = get_rankers(configs=ranker_configs, service_context=service_context)
 
         return SimpleEngine(retriever=retriever, node_postprocessors=rankers)
@@ -58,3 +56,8 @@ class SimpleEngine(RetrieverQueryEngine):
         """Allow query to be str"""
         query_bundle = QueryBundle(query) if isinstance(query, str) else query
         return await super().aretrieve(query_bundle)
+
+    def add_docs(self, input_files: list[str]):
+        documents = SimpleDirectoryReader(input_files=input_files).load_data()
+        retriever: RAGRetriever = self.retriever
+        retriever.add_docs(documents)
diff --git a/metagpt/rag/llm.py b/metagpt/rag/llm.py
index e67be1416..405b29991 100644
--- a/metagpt/rag/llm.py
+++ b/metagpt/rag/llm.py
@@ -4,4 +4,4 @@ from metagpt.config2 import config
 
 
 def get_default_llm() -> OpenAI:
-    return OpenAI(api_base=config.llm.base_url, api_key=config.llm.api_key)
+    return OpenAI(api_base=config.llm.base_url, api_key=config.llm.api_key, model=config.llm.model)
diff --git a/metagpt/rag/rankers/__init__.py b/metagpt/rag/rankers/__init__.py
index 5bfa866ef..bb14007ba 100644
--- a/metagpt/rag/rankers/__init__.py
+++ b/metagpt/rag/rankers/__init__.py
@@ -1,34 +1,6 @@
-"""init"""
-from metagpt.rag.schema import RankerConfig, LLMRankerConfig
-from llama_index import ServiceContext
-from llama_index.postprocessor import LLMRerank
-from llama_index.postprocessor.types import BaseNodePostprocessor
+"""Rankers init"""
+
+from metagpt.rag.rankers.factory import get_rankers
 
 
-def get_rankers(
-    configs: list[RankerConfig] = None, service_context: ServiceContext = None
-) -> list[BaseNodePostprocessor]:
-    if not configs:
-        return [_default_ranker(service_context)]
-
-    return [_get_ranker(config, service_context) for config in configs]
-
-
-def _default_ranker(service_context: ServiceContext = None):
-    return LLMRerank(top_n=LLMRankerConfig().top_n, service_context=service_context)
-
-
-def _get_ranker(config: RankerConfig, service_context: ServiceContext = None):
-    ranker_factory = {
-        LLMRankerConfig: _create_llm_ranker,
-    }
-
-    create_func = ranker_factory.get(type(config))
-    if create_func:
-        return create_func(config, service_context)
-
-    raise ValueError(f"Unknown ranker config: {config}")
-
-
-def _create_llm_ranker(config, service_context=None):
-    return LLMRerank(top_n=config.top_n, service_context=service_context)
+__all__ = ["get_rankers"]
diff --git a/metagpt/rag/rankers/factory.py b/metagpt/rag/rankers/factory.py
new file mode 100644
index 000000000..14dc89604
--- /dev/null
+++ b/metagpt/rag/rankers/factory.py
@@ -0,0 +1,36 @@
+from llama_index import ServiceContext
+from llama_index.postprocessor import LLMRerank
+from llama_index.postprocessor.types import BaseNodePostprocessor
+
+from metagpt.rag.schema import LLMRankerConfig, RankerConfigType
+
+
+class RankerFactory:
+    def __init__(self):
+        self.ranker_creators = {
+            LLMRankerConfig: self._create_llm_ranker,
+        }
+
+    def get_rankers(
+        self, configs: list[RankerConfigType] = None, service_context: ServiceContext = None
+    ) -> list[BaseNodePostprocessor]:
+        if not configs:
+            return [self._default_ranker(service_context)]
+
+        return [self._get_ranker(config, service_context) for config in configs]
+
+    def _default_ranker(self, service_context: ServiceContext = None):
+        return LLMRerank(top_n=LLMRankerConfig().top_n, service_context=service_context)
+
+    def _get_ranker(self, config: RankerConfigType, service_context: ServiceContext = None):
+        create_func = self.ranker_creators.get(type(config))
+        if create_func:
+            return create_func(config, service_context)
+
+        raise ValueError(f"Unknown ranker config: {config}")
+
+    def _create_llm_ranker(self, config, service_context=None):
+        return LLMRerank(top_n=config.top_n, service_context=service_context)
+
+
+get_rankers = RankerFactory().get_rankers
diff --git a/metagpt/rag/retrievers/__init__.py b/metagpt/rag/retrievers/__init__.py
index 3f9098e35..88cb4cc77 100644
--- a/metagpt/rag/retrievers/__init__.py
+++ b/metagpt/rag/retrievers/__init__.py
@@ -1,55 +1,6 @@
+"""Retrievers init"""
+
+from metagpt.rag.retrievers.hybrid_retriever import SimpleHybridRetriever
+from metagpt.rag.retrievers.factory import get_retriever
+
 __all__ = ["SimpleHybridRetriever", "get_retriever"]
-
-from llama_index import (
-    ServiceContext,
-    StorageContext,
-    VectorStoreIndex,
-)
-from llama_index.retrievers import BaseRetriever, BM25Retriever, VectorIndexRetriever
-from llama_index.schema import BaseNode
-from llama_index.vector_stores.faiss import FaissVectorStore
-
-from metagpt.rag.retrievers.hybrid import SimpleHybridRetriever
-from metagpt.rag.schema import RetrieverConfig, FAISSRetrieverConfig, BM25RetrieverConfig
-import faiss
-
-
-def get_retriever(
-    nodes: list[BaseNode], configs: list[RetrieverConfig] = None, service_context: ServiceContext = None
-) -> BaseRetriever:
-    if not configs:
-        return _default_retriever(nodes, service_context)
-
-    retrivers = [_get_retriever(nodes, config, service_context) for config in configs]
-
-    return SimpleHybridRetriever(*retrivers, service_context=service_context) if len(retrivers) > 1 else retrivers[0]
-
-
-def _default_retriever(nodes: list[BaseNode], service_context: ServiceContext = None) -> BaseRetriever:
-    return VectorStoreIndex(nodes=nodes, service_context=service_context).as_retriever()
-
-
-def _get_retriever(
-    nodes: list[BaseNode], config: RetrieverConfig, service_context: ServiceContext = None
-) -> BaseRetriever:
-    retriever_factory = {
-        FAISSRetrieverConfig: _create_faiss_retriever,
-        BM25RetrieverConfig: _create_bm25_retriever,
-    }
-
-    create_func = retriever_factory.get(type(config))
-    if create_func:
-        return create_func(nodes, config, service_context)
-
-    raise ValueError(f"Unknown retriever config: {config}")
-
-
-def _create_faiss_retriever(nodes: list[BaseNode], config: RetrieverConfig, service_context: ServiceContext):
-    vector_store = FaissVectorStore(faiss_index=faiss.IndexFlatL2(config.dimensions))
-    storage_context = StorageContext.from_defaults(vector_store=vector_store)
-    vector_index = VectorStoreIndex(nodes=nodes, storage_context=storage_context, service_context=service_context)
-    return VectorIndexRetriever(index=vector_index, similarity_top_k=config.similarity_top_k)
-
-
-def _create_bm25_retriever(nodes: list[BaseNode], config: RetrieverConfig, service_context: ServiceContext = None):
-    return BM25Retriever.from_defaults(**config.model_dump(), nodes=nodes)
diff --git a/metagpt/rag/retrievers/base.py b/metagpt/rag/retrievers/base.py
index c0291f217..535e427c3 100644
--- a/metagpt/rag/retrievers/base.py
+++ b/metagpt/rag/retrievers/base.py
@@ -3,6 +3,7 @@
 
 from abc import abstractmethod
 
+from llama_index import Document
 from llama_index.retrievers import BaseRetriever
 from llama_index.schema import NodeWithScore, QueryType
 
@@ -14,5 +15,9 @@ class RAGRetriever(BaseRetriever):
     async def _aretrieve(self, query: QueryType) -> list[NodeWithScore]:
         """retrieve nodes"""
 
+    @abstractmethod
+    def add_docs(self, documents: list[Document]) -> None:
+        """add docs"""
+
     def _retrieve(self, query: QueryType) -> list[NodeWithScore]:
         """retrieve nodes"""
diff --git a/metagpt/rag/retrievers/bm25_retriever.py b/metagpt/rag/retrievers/bm25_retriever.py
new file mode 100644
index 000000000..4141827dd
--- /dev/null
+++ b/metagpt/rag/retrievers/bm25_retriever.py
@@ -0,0 +1,14 @@
+from llama_index import Document
+from llama_index.retrievers import BM25Retriever
+
+
+class DynamicBM25Retriever(BM25Retriever):
+    def add_docs(self, documents: list[Document]):
+        try:
+            from rank_bm25 import BM25Okapi
+        except ImportError:
+            raise ImportError("Please install rank_bm25: pip install rank-bm25")
+
+        self._nodes.extend(documents)
+        self._corpus = [self._tokenizer(node.get_content()) for node in self._nodes]
+        self.bm25 = BM25Okapi(self._corpus)
diff --git a/metagpt/rag/retrievers/factory.py b/metagpt/rag/retrievers/factory.py
new file mode 100644
index 000000000..cde70e219
--- /dev/null
+++ b/metagpt/rag/retrievers/factory.py
@@ -0,0 +1,60 @@
+import faiss
+from llama_index import StorageContext, VectorStoreIndex
+from llama_index.indices.base import BaseIndex
+from llama_index.vector_stores.faiss import FaissVectorStore
+
+from metagpt.rag.retrievers.base import RAGRetriever
+from metagpt.rag.retrievers.bm25_retriever import DynamicBM25Retriever
+from metagpt.rag.retrievers.faiss_retriever import FAISSRetriever
+from metagpt.rag.retrievers.hybrid_retriever import SimpleHybridRetriever
+from metagpt.rag.schema import (
+    BM25RetrieverConfig,
+    FAISSRetrieverConfig,
+    RetrieverConfigType,
+)
+
+
+class RetrieverFactory:
+    def __init__(self):
+        self.retriever_creators = {
+            FAISSRetrieverConfig: self._create_faiss_retriever,
+            BM25RetrieverConfig: self._create_bm25_retriever,
+        }
+
+    def get_retriever(self, index: BaseIndex, configs: list[RetrieverConfigType] = None) -> RAGRetriever:
+        if not configs:
+            return self._default_retriever(index)
+
+        retrievers = [self._get_retriever(index, config) for config in configs]
+
+        return (
+            SimpleHybridRetriever(*retrievers, service_context=index.service_context)
+            if len(retrievers) > 1
+            else retrievers[0]
+        )
+
+    def _default_retriever(self, index: BaseIndex) -> RAGRetriever:
+        return index.as_retriever()
+
+    def _get_retriever(self, index: BaseIndex, config: RetrieverConfigType) -> RAGRetriever:
+        create_func = self.retriever_creators.get(type(config))
+        if create_func:
+            return create_func(index, config)
+
+        raise ValueError(f"Unknown retriever config: {config}")
+
+    def _create_faiss_retriever(self, index: BaseIndex, config: FAISSRetrieverConfig):
+        vector_store = FaissVectorStore(faiss_index=faiss.IndexFlatL2(config.dimensions))
+        storage_context = StorageContext.from_defaults(vector_store=vector_store)
+        vector_index = VectorStoreIndex(
+            nodes=list(index.docstore.docs.values()),
+            storage_context=storage_context,
+            service_context=index.service_context,
+        )
+        return FAISSRetriever(vector_index, **config.model_dump())
+
+    def _create_bm25_retriever(self, index: BaseIndex, config: BM25RetrieverConfig):
+        return DynamicBM25Retriever.from_defaults(**config.model_dump(), index=index)
+
+
+get_retriever = RetrieverFactory().get_retriever
diff --git a/metagpt/rag/retrievers/faiss_retriever.py b/metagpt/rag/retrievers/faiss_retriever.py
new file mode 100644
index 000000000..9888959e1
--- /dev/null
+++ b/metagpt/rag/retrievers/faiss_retriever.py
@@ -0,0 +1,8 @@
+from llama_index import Document
+from llama_index.retrievers import VectorIndexRetriever
+
+
+class FAISSRetriever(VectorIndexRetriever):
+    def add_docs(self, documents: list[Document]):
+        for document in documents:
+            self._index.insert(document)
diff --git a/metagpt/rag/retrievers/hybrid.py b/metagpt/rag/retrievers/hybrid_retriever.py
similarity index 88%
rename from metagpt/rag/retrievers/hybrid.py
rename to metagpt/rag/retrievers/hybrid_retriever.py
index 701b13aa2..f4e9c3479 100644
--- a/metagpt/rag/retrievers/hybrid.py
+++ b/metagpt/rag/retrievers/hybrid_retriever.py
@@ -1,5 +1,5 @@
 """Hybrid retriever."""
-from llama_index import ServiceContext
+from llama_index import Document, ServiceContext
 from llama_index.schema import QueryType
 
 from metagpt.rag.retrievers.base import RAGRetriever
@@ -36,3 +36,7 @@ class SimpleHybridRetriever(RAGRetriever):
                 result.append(n)
                 node_ids.add(n.node.node_id)
         return result
+
+    def add_docs(self, documents: list[Document]):
+        for r in self.retrievers:
+            r.add_docs(documents)
diff --git a/metagpt/rag/schema.py b/metagpt/rag/schema.py
index e781cc2ab..9eb76d43d 100644
--- a/metagpt/rag/schema.py
+++ b/metagpt/rag/schema.py
@@ -1,5 +1,7 @@
 """Retriever schemas"""
 
+from typing import Union
+
 from pydantic import BaseModel
 
 
@@ -21,3 +23,7 @@ class RankerConfig(BaseModel):
 
 class LLMRankerConfig(RankerConfig):
     ...
+
+
+RetrieverConfigType = Union[FAISSRetrieverConfig, BM25RetrieverConfig]
+RankerConfigType = LLMRankerConfig