diff --git a/vnpy/trader/engine.py b/vnpy/trader/engine.py
index 9b60bae0..9a65e90d 100644
--- a/vnpy/trader/engine.py
+++ b/vnpy/trader/engine.py
@@ -299,7 +299,7 @@ class LogEngine(BaseEngine):
         file_path = log_path.joinpath(filename)
 
         file_handler = logging.FileHandler(
-            file_path, mode="w", encoding="utf8"
+            file_path, mode="a", encoding="utf8"
         )
         file_handler.setLevel(self.level)
         file_handler.setFormatter(self.formatter)