diff --git a/metagpt/rag/factories/index.py b/metagpt/rag/factories/index.py
index 3e0c13c25..504faafc6 100644
--- a/metagpt/rag/factories/index.py
+++ b/metagpt/rag/factories/index.py
@@ -23,11 +23,11 @@ class RAGIndexFactory(ConfigFactory):
         """Key is PersistType."""
         return super().get_instance(config, **kwargs)
 
-    def extract_embed_model(self, config, **kwargs) -> BaseEmbedding:
+    def _extract_embed_model(self, config, **kwargs) -> BaseEmbedding:
         return self._val_from_config_or_kwargs("embed_model", config, **kwargs)
 
     def _create_faiss(self, config: FAISSIndexConfig, **kwargs) -> VectorStoreIndex:
-        embed_model = self.extract_embed_model(config, **kwargs)
+        embed_model = self._extract_embed_model(config, **kwargs)
 
         vector_store = FaissVectorStore.from_persist_dir(str(config.persist_path))
         storage_context = StorageContext.from_defaults(vector_store=vector_store, persist_dir=config.persist_path)
@@ -35,7 +35,7 @@ class RAGIndexFactory(ConfigFactory):
         return index
 
     def _create_chroma(self, config: ChromaIndexConfig, **kwargs) -> VectorStoreIndex:
-        embed_model = self.extract_embed_model(config, **kwargs)
+        embed_model = self._extract_embed_model(config, **kwargs)
 
         db = chromadb.PersistentClient(str(config.persist_path))
         chroma_collection = db.get_or_create_collection(config.collection_name)