diff --git a/apps/wpm/serializers.py b/apps/wpm/serializers.py
index ced00f66..7e035c52 100644
--- a/apps/wpm/serializers.py
+++ b/apps/wpm/serializers.py
@@ -25,6 +25,7 @@ from apps.qm.serializers import FtestProcessSerializer
 import logging
 from apps.qm.models import Defect
 from apps.utils.snowflake import idWorker
+from decimal import Decimal
 mylogger = logging.getLogger("log")
 
 class OtherLogSerializer(CustomModelSerializer):
@@ -200,7 +201,7 @@ class WMaterialSerializer(CustomModelSerializer):
     
     def to_representation(self, instance):
         ret = super().to_representation(instance)
-        ret['count_cando'] = ret['count'] - ret['count_working']
+        ret['count_cando'] = str(Decimal(ret['count']) - Decimal(ret['count_working']))
         return ret
 
 class MlogbDefectSerializer(CustomModelSerializer):