diff --git a/tools/azure-sdk-tools/packaging_tools/change_log.py b/tools/azure-sdk-tools/packaging_tools/change_log.py
index 64d2ebe0b6b2..10fc7ae47fff 100644
--- a/tools/azure-sdk-tools/packaging_tools/change_log.py
+++ b/tools/azure-sdk-tools/packaging_tools/change_log.py
@@ -142,7 +142,8 @@ def models(self, diff_entry):
 def build_change_log(old_report, new_report):
     change_log = ChangeLog(old_report, new_report)
 
-    result = diff(old_report, new_report)
+    # when diff result is large,  compare_lengths=True may cause wrong result
+    result = diff(old_report, new_report, compare_lengths=False)
 
     for diff_line in result:
         # Operations