diff --git a/data_structures.py b/data_structures.py
index 01cbf01..01f1651 100644
--- a/data_structures.py
+++ b/data_structures.py
@@ -116,6 +116,12 @@ class DataStructures:
         :return: 评价指标值
         """
         cost, tardiness = objectives
-        cost_ratio = cost/(max_cost - optimal_cost)
-        tardiness_ratio = tardiness/( max_tardiness - optimal_tardiness)
+        if max_cost - optimal_cost == 0:
+            cost_ratio = 0
+        else:
+            cost_ratio = cost/(max_cost - optimal_cost)
+        if max_tardiness - optimal_tardiness == 0:
+            tardiness_ratio = 0
+        else:
+            tardiness_ratio = tardiness/( max_tardiness - optimal_tardiness)
         return cost_ratio + tardiness_ratio
\ No newline at end of file