diff --git a/src/agentscope/models/response.py b/src/agentscope/models/response.py
index b034a4197..661ccaeac 100644
--- a/src/agentscope/models/response.py
+++ b/src/agentscope/models/response.py
@@ -53,7 +53,7 @@ def text(self) -> str:
         if self._text is None:
             if self.stream is not None:
                 for _, chunk in self.stream:
-                    self._text += chunk
+                    self._text = chunk
         return self._text
 
     @text.setter