diff --git a/metagpt/memory/longterm_memory.py b/metagpt/memory/longterm_memory.py
index 926c845cb..8521c046b 100644
--- a/metagpt/memory/longterm_memory.py
+++ b/metagpt/memory/longterm_memory.py
@@ -43,17 +43,24 @@ class LongTermMemory(Memory):
                 # and ignore adding messages from recover repeatedly
                 self.memory_storage.add(message)
 
-    def remember(self, observed: list[Message], k=0) -> list[Message]:
-        """remember the most similar k memories from observed Messages, return all when k=0"""
+    def remember(self, observed: list[Message], k=10) -> list[Message]:
+        """
+        remember the most similar k memories from observed Messages, return all when k=0
+            1. remember the short-term memory(stm) news
+            2. integrate the stm news with ltm(long-term memory) news
+        """
+        stm_news = super(LongTermMemory, self).remember(observed)  # shot-term memory news
         if not self.memory_storage.is_initialized:
-            # memory_storage hasn't initialized, use default `remember`
-            return super(LongTermMemory, self).remember(observed)
+            # memory_storage hasn't initialized, use default `remember` to get stm_news
+            return stm_news
 
-        news: list[Message] = []
-        for mem in observed:
+        ltm_news: list[Message] = []
+        for mem in stm_news:
+            # integrate stm & ltm
             mem_searched = self.memory_storage.search(mem)
-            news.extend(mem_searched)
-        return news[-k:]
+            if len(mem_searched) > 0:
+                ltm_news.append(mem)
+        return ltm_news[-k:]
 
     def delete(self, message: Message):
         super(LongTermMemory, self).delete(message)
diff --git a/metagpt/memory/memory.py b/metagpt/memory/memory.py
index a96aaf1be..5d3b736a3 100644
--- a/metagpt/memory/memory.py
+++ b/metagpt/memory/memory.py
@@ -63,7 +63,7 @@ class Memory:
         """Return the most recent k memories, return all when k=0"""
         return self.storage[-k:]
 
-    def remember(self, observed: list[Message], k=0) -> list[Message]:
+    def remember(self, observed: list[Message], k=10) -> list[Message]:
         """remember the most recent k memories from observed Messages, return all when k=0"""
         already_observed = self.get(k)
         news: list[Message] = []
diff --git a/tests/metagpt/memory/test_longterm_memory.py b/tests/metagpt/memory/test_longterm_memory.py
new file mode 100644
index 000000000..62a3a2361
--- /dev/null
+++ b/tests/metagpt/memory/test_longterm_memory.py
@@ -0,0 +1,55 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+# @Desc   : unittest of `metagpt/memory/longterm_memory.py`
+
+from metagpt.config import CONFIG
+from metagpt.schema import Message
+from metagpt.actions import BossRequirement
+from metagpt.roles.role import RoleContext
+from metagpt.memory import LongTermMemory
+
+
+def test_ltm_search():
+    assert hasattr(CONFIG, "long_term_memory") is True
+    openai_api_key = CONFIG.openai_api_key
+    assert len(openai_api_key) > 20
+
+    role_id = 'UTUserLtm(Product Manager)'
+    rc = RoleContext(watch=[BossRequirement])
+    ltm = LongTermMemory()
+    ltm.recover_memory(role_id, rc)
+
+    idea = 'Write a cli snake game'
+    message = Message(role='BOSS', content=idea, cause_by=BossRequirement)
+    news = ltm.remember([message])
+    assert len(news) == 1
+    ltm.add(message)
+
+    sim_idea = 'Write a game of cli snake'
+    sim_message = Message(role='BOSS', content=sim_idea, cause_by=BossRequirement)
+    news = ltm.remember([sim_message])
+    assert len(news) == 0
+    ltm.add(sim_message)
+
+    new_idea = 'Write a 2048 web game'
+    new_message = Message(role='BOSS', content=new_idea, cause_by=BossRequirement)
+    news = ltm.remember([new_message])
+    assert len(news) == 1
+    ltm.add(new_message)
+
+    # restore from local index
+    ltm_new = LongTermMemory()
+    ltm_new.recover_memory(role_id, rc)
+    news = ltm_new.remember([message])
+    assert len(news) == 0
+
+    ltm_new.recover_memory(role_id, rc)
+    news = ltm_new.remember([sim_message])
+    assert len(news) == 0
+
+    new_idea = 'Write a Battle City'
+    new_message = Message(role='BOSS', content=new_idea, cause_by=BossRequirement)
+    news = ltm_new.remember([new_message])
+    assert len(news) == 1
+
+    ltm_new.clear()
diff --git a/tests/metagpt/memory/test_memory_storage.py b/tests/metagpt/memory/test_memory_storage.py
index 4e59fb003..6bb3e8f1d 100644
--- a/tests/metagpt/memory/test_memory_storage.py
+++ b/tests/metagpt/memory/test_memory_storage.py
@@ -2,8 +2,7 @@
 # -*- coding: utf-8 -*-
 # @Desc   : the unittests of metagpt/memory/memory_storage.py
 
-from typing import List, Tuple
-import pytest
+from typing import List
 
 from metagpt.memory.memory_storage import MemoryStorage
 from metagpt.schema import Message