diff --git a/metagpt/provider/openai_api.py b/metagpt/provider/openai_api.py
index 8f8d45d73..11f429601 100644
--- a/metagpt/provider/openai_api.py
+++ b/metagpt/provider/openai_api.py
@@ -262,10 +262,10 @@ class OpenAIGPTAPI(BaseGPTAPI, RateLimiter):
         self._update_costs(rsp.get("usage"))
         return rsp
 
-    def _process_message(self, messages: Union[str, Message, list[dict]]) -> list[dict]:
+    def _process_message(self, messages: Union[str, Message, list[dict], list[Message]]) -> list[dict]:
         """convert messages to list[dict]."""
         if isinstance(messages, list):
-            return messages
+            return [msg if isinstance(msg, dict) else msg.to_dict() for msg in messages]
 
         if isinstance(messages, Message):
             messages = [messages.to_dict()]
diff --git a/tests/metagpt/provider/test_openai.py b/tests/metagpt/provider/test_openai.py
index d6d9f4f9d..93ac6623c 100644
--- a/tests/metagpt/provider/test_openai.py
+++ b/tests/metagpt/provider/test_openai.py
@@ -59,3 +59,12 @@ def test_ask_code_Message():
     assert "language" in rsp
     assert "code" in rsp
     assert len(rsp["code"]) > 0
+
+
+def test_ask_code_list_Message():
+    llm = OpenAIGPTAPI()
+    msg = [UserMessage("a=[1,2,5,10,-10]"), UserMessage("写出求a中最大值的代码python")]
+    rsp = llm.ask_code(msg)  # -> {'language': 'python', 'code': 'max_value = max(a)\nmax_value'}
+    assert "language" in rsp
+    assert "code" in rsp
+    assert len(rsp["code"]) > 0