diff --git a/IRaCIS.Core.Application/Service/ReadingCalculate/PCWG3CalculateService.cs b/IRaCIS.Core.Application/Service/ReadingCalculate/PCWG3CalculateService.cs
index 5905518d8..ced5c5a11 100644
--- a/IRaCIS.Core.Application/Service/ReadingCalculate/PCWG3CalculateService.cs
+++ b/IRaCIS.Core.Application/Service/ReadingCalculate/PCWG3CalculateService.cs
@@ -1313,7 +1313,14 @@ namespace IRaCIS.Core.Application.Service.ReadingCalculate
                         // V3与V2的间隔 >= 6周
 
                         // 按上面条件写三个if看着清晰点
-                        if (lastNewLesionsCount + lastBTN - lastTwoBTN >= 2)
+
+                        var lastBtnSubMin = lastBTN - lastTwoBTN;
+                        if (lastBtnSubMin < 0)
+                        {
+                            lastBtnSubMin = 0;
+                        }
+
+                        if (lastNewLesionsCount + lastBtnSubMin >= 2)
                         {
                             if (thisNewBoneLesionsCount + btnValue + thisNewLesionsCount >= 2)
                             {