diff --git a/metagpt/const.py b/metagpt/const.py
index c53e8494a..e7a0dc31b 100644
--- a/metagpt/const.py
+++ b/metagpt/const.py
@@ -157,3 +157,6 @@ SWE_SETUP_PATH = get_metagpt_package_root() / "metagpt/tools/swe_agent_commands/
 
 # experience pool
 EXPERIENCE_MASK = "<experience>"
+
+# Used to identify user requirements in the memory index.
+USER_REQUIREMENT = "metagpt.actions.add_requirement.UserRequirement"
diff --git a/metagpt/roles/di/role_zero.py b/metagpt/roles/di/role_zero.py
index 5818bc1f3..9e64a1954 100644
--- a/metagpt/roles/di/role_zero.py
+++ b/metagpt/roles/di/role_zero.py
@@ -13,7 +13,7 @@ from metagpt.actions import Action, UserRequirement
 from metagpt.actions.analyze_requirements import AnalyzeRequirementsRestrictions
 from metagpt.actions.di.run_command import RunCommand
 from metagpt.actions.search_enhanced_qa import SearchEnhancedQA
-from metagpt.const import IMAGES
+from metagpt.const import IMAGES, USER_REQUIREMENT
 from metagpt.exp_pool import exp_cache
 from metagpt.exp_pool.context_builders import RoleZeroContextBuilder
 from metagpt.exp_pool.serializers import RoleZeroSerializer
@@ -602,10 +602,10 @@ class RoleZero(Role):
 
         memories = self.rc.memory.get(k)
 
-        if not self._should_use_longterm_memory(k=k, k_memories=memories):
+        if not self._should_use_longterm_memory(k=k):
             return memories
 
-        query = self._build_longterm_memory_query(memories)
+        query = self._build_longterm_memory_query()
         related_memories = self.longterm_memory.fetch(query)
         logger.info(f"Fetched {len(related_memories)} long-term memories.")
 
@@ -625,19 +625,17 @@ class RoleZero(Role):
 
         self._transfer_to_longterm_memory()
 
-    def _should_use_longterm_memory(self, k: int = None, k_memories: list[Message] = None) -> bool:
+    def _should_use_longterm_memory(self, k: int = None) -> bool:
         """Determines if long-term memory should be used.
 
         Long-term memory is used if:
         - k is not 0.
-        - k_memories is None or k_memories is not empty, and the last message is a user message.
         - Long-term memory usage is enabled.
         - The count of recent memories is greater than self.memory_k.
         """
 
         conds = [
             k != 0,
-            k_memories is None or self._is_last_message_from_user(k_memories),
             self.enable_longterm_memory,
             self.rc.memory.count() > self.memory_k,
         ]
@@ -662,16 +660,19 @@ class RoleZero(Role):
 
         return LongTermMemoryItem(user_message=user_message, ai_message=message)
 
-    def _is_last_message_from_user(self, memories: list[Message]) -> bool:
-        return bool(memories and memories[-1].is_user_message())
-
     def _is_first_message_from_ai(self, memories: list[Message]) -> bool:
         return bool(memories and memories[0].is_ai_message())
 
-    def _build_longterm_memory_query(self, memories: list[Message]) -> str:
+    def _build_longterm_memory_query(self) -> str:
         """Build the content used to query related long-term memory.
 
         Default is to get the most recent user message, or an empty string if none is found.
         """
+        message = self._get_the_last_user_message()
 
-        return next((m.content for m in reversed(memories) if m.is_real_user_message()), "")
+        return message.content if message else ""
+
+    def _get_the_last_user_message(self) -> Message:
+        values = self.rc.memory.index.get(USER_REQUIREMENT, [])
+
+        return values[-1] if values else None
diff --git a/metagpt/schema.py b/metagpt/schema.py
index 8481bccf3..9352664e2 100644
--- a/metagpt/schema.py
+++ b/metagpt/schema.py
@@ -415,9 +415,6 @@ class Message(BaseModel):
     def is_ai_message(self) -> bool:
         return self.role == "assistant"
 
-    def is_real_user_message(self) -> bool:
-        return self.is_user_message() and "UserRequirement" in self.cause_by
-
 
 class UserMessage(Message):
     """便于支持OpenAI的消息
diff --git a/tests/metagpt/roles/di/test_role_zero.py b/tests/metagpt/roles/di/test_role_zero.py
index 964d456a7..0d427ce0f 100644
--- a/tests/metagpt/roles/di/test_role_zero.py
+++ b/tests/metagpt/roles/di/test_role_zero.py
@@ -101,7 +101,7 @@ class TestRoleZero:
         mock_role_zero.rc.memory.get.assert_called_once_with(really_k)
 
         if k != 0:
-            mock_role_zero._should_use_longterm_memory.assert_called_once_with(k=really_k, k_memories=memories)
+            mock_role_zero._should_use_longterm_memory.assert_called_once_with(k=really_k)
 
             if should_use_ltm:
                 mock_role_zero.longterm_memory.fetch.assert_called_once_with("user")
@@ -174,18 +174,6 @@ class TestRoleZero:
         mock_role_zero.rc.memory.get_by_position.assert_any_call(-(mock_role_zero.memory_k + 1))
         mock_role_zero.rc.memory.get_by_position.assert_any_call(-(mock_role_zero.memory_k + 2))
 
-    @pytest.mark.parametrize(
-        "memories,expected",
-        [
-            ([UserMessage(content="user")], True),
-            ([AIMessage(content="ai")], False),
-            ([], False),
-        ],
-    )
-    def test_is_last_message_from_user(self, mock_role_zero: RoleZero, memories, expected):
-        result = mock_role_zero._is_last_message_from_user(memories)
-        assert result == expected
-
     @pytest.mark.parametrize(
         "memories,expected",
         [