diff --git a/metagpt/memory/brain_memory.py b/metagpt/memory/brain_memory.py
index 9d1b038bb..cb67fea8e 100644
--- a/metagpt/memory/brain_memory.py
+++ b/metagpt/memory/brain_memory.py
@@ -1,10 +1,11 @@
 from enum import Enum
-from typing import List
+from typing import List, Dict
 
 import pydantic
 
 from metagpt import Message
 
+
 class MessageType(Enum):
     Talk = "TALK"
     Solution = "SOLUTION"
@@ -14,29 +15,28 @@ class MessageType(Enum):
 
 
 class BrainMemory(pydantic.BaseModel):
-    history: List[Message] = []
-    stack: List[Message] = []
-    solution: List[Message] = []
-    knowledge: List[Message] = []
-
+    history: List[Dict] = []
+    stack: List[Dict] = []
+    solution: List[Dict] = []
+    knowledge: List[Dict] = []
 
     def add_talk(self, msg: Message):
         msg.add_tag(MessageType.Talk.value)
-        self.history.append(msg)
+        self.history.append(msg.dict())
 
     def add_answer(self, msg: Message):
         msg.add_tag(MessageType.Answer.value)
-        self.history.append(msg)
+        self.history.append(msg.dict())
 
     def get_knowledge(self) -> str:
-        texts = [k.content for k in self.knowledge]
+        texts = [Message(**m).content for m in self.knowledge]
         return "\n".join(texts)
 
     @property
     def history_text(self):
         if len(self.history) == 0:
             return ""
-        texts = [m.content for m in self.history[:-1]]
+        texts = [Message(**m).content for m in self.history[:-1]]
         return "\n".join(texts)
 
     def move_to_solution(self):
@@ -44,7 +44,7 @@ class BrainMemory(pydantic.BaseModel):
             return
         msgs = self.history[:-1]
         self.solution.extend(msgs)
-        if not self.history[-1].is_contain(MessageType.Talk.value):
+        if not Message(**self.history[-1]).is_contain(MessageType.Talk.value):
             self.solution.append(self.history[-1])
             self.history = []
         else:
@@ -52,7 +52,9 @@ class BrainMemory(pydantic.BaseModel):
 
     @property
     def last_talk(self):
-        if len(self.history) == 0 or not self.history[-1].is_contain_tags([MessageType.Talk.value]):
+        if len(self.history) == 0:
             return None
-        return self.history[-1].content
-
+        last_msg = Message(**self.history[-1])
+        if not last_msg.is_contain(MessageType.Talk.value):
+            return None
+        return last_msg.content
diff --git a/metagpt/roles/assistant.py b/metagpt/roles/assistant.py
index 199cdcafd..4519fcdb8 100644
--- a/metagpt/roles/assistant.py
+++ b/metagpt/roles/assistant.py
@@ -77,7 +77,7 @@ class Assistant(Role):
         return output
 
     async def talk(self, text):
-        self.memory.add_talk(Message(content=text, tags=set([MessageType.Talk.value])))
+        self.memory.add_talk(Message(content=text))
 
     async def _plan(self, rsp: str, **kwargs) -> bool:
         skill, text = Assistant.extract_info(input_string=rsp)
diff --git a/metagpt/schema.py b/metagpt/schema.py
index 909313886..4d7f0cc21 100644
--- a/metagpt/schema.py
+++ b/metagpt/schema.py
@@ -70,6 +70,22 @@ class Message:
     def is_contain(self, tag):
         return self.is_contain_tags([tag])
 
+    def dict(self):
+        """pydantic-like `dict` function"""
+        full = {
+            "instruct_content": self.instruct_content,
+            "cause_by": self.cause_by,
+            "sent_from": self.sent_from,
+            "send_to": self.send_to,
+            "tags": self.tags
+        }
+
+        m = {"content": self.content}
+        for k, v in full.items():
+            if v:
+                m[k] = v
+        return m
+
 
 @dataclass
 class UserMessage(Message):
@@ -101,7 +117,6 @@ class AIMessage(Message):
         super().__init__(content, 'assistant')
 
 
-
 if __name__ == '__main__':
     test_content = 'test_message'
     msgs = [
diff --git a/tests/metagpt/memory/test_brain_memory.py b/tests/metagpt/memory/test_brain_memory.py
new file mode 100644
index 000000000..b5fc942ca
--- /dev/null
+++ b/tests/metagpt/memory/test_brain_memory.py
@@ -0,0 +1,57 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+"""
+@Time    : 2023/8/27
+@Author  : mashenquan
+@File    : test_brain_memory.py
+"""
+import json
+from typing import List
+
+import pydantic
+
+from metagpt.memory.brain_memory import BrainMemory
+from metagpt.schema import Message
+
+
+def test_json():
+    class Input(pydantic.BaseModel):
+        history: List[str]
+        solution: List[str]
+        knowledge: List[str]
+        stack: List[str]
+
+    inputs = [
+        {
+            "history": ["a", "b"],
+            "solution": ["c"],
+            "knowledge": ["d", "e"],
+            "stack": ["f"]
+        }
+    ]
+
+    for i in inputs:
+        v = Input(**i)
+        bm = BrainMemory()
+        for h in v.history:
+            msg = Message(content=h)
+            bm.history.append(msg.dict())
+        for h in v.solution:
+            msg = Message(content=h)
+            bm.solution.append(msg.dict())
+        for h in v.knowledge:
+            msg = Message(content=h)
+            bm.knowledge.append(msg.dict())
+        for h in v.stack:
+            msg = Message(content=h)
+            bm.stack.append(msg.dict())
+        s = bm.json()
+        m = json.loads(s)
+        bm = BrainMemory(**m)
+        assert bm
+        for v in bm.history:
+            msg = Message(**v)
+            assert msg
+
+if __name__ == '__main__':
+    test_json()
\ No newline at end of file