diff --git a/httprunner/report.py b/httprunner/report.py
index a3d775d4..19e45718 100644
--- a/httprunner/report.py
+++ b/httprunner/report.py
@@ -80,16 +80,15 @@ def aggregate_stat(origin_stat, new_stat):
     for key in new_stat:
         if key not in origin_stat:
             origin_stat[key] = new_stat[key]
-
+        elif key == "start_at":
+            # start datetime
+            origin_stat["start_at"] = min(origin_stat["start_at"], new_stat["start_at"])
         elif key == "duration":
             # duration = max_end_time - min_start_time
             max_end_time = max(origin_stat["start_at"] + origin_stat["duration"],
                                new_stat["start_at"] + new_stat["duration"])
             min_start_time = min(origin_stat["start_at"], new_stat["start_at"])
             origin_stat["duration"] = max_end_time - min_start_time
-        elif key == "start_at":
-            # start datetime
-            origin_stat["start_at"] = min(origin_stat["start_at"], new_stat["start_at"])
         else:
             origin_stat[key] += new_stat[key]