diff --git a/trunk/src/app/srs_app_log.cpp b/trunk/src/app/srs_app_log.cpp
index 67f26930ba..1c0a5dfd15 100644
--- a/trunk/src/app/srs_app_log.cpp
+++ b/trunk/src/app/srs_app_log.cpp
@@ -414,7 +414,7 @@ void SrsFastLog::open_log_file()
     
     if(fd == -1 && errno == ENOENT) {
         fd = open(filename.c_str(), 
-            O_RDWR | O_CREAT | O_TRUNC, 
+            O_RDWR | O_CREAT | O_TRUNC | O_APPEND/*logrotate copytruncate need this flag*/, 
             S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH
         );
     }