diff --git a/Tiobon.Core.Services/Ghre/Ghre_CourseServices.cs b/Tiobon.Core.Services/Ghre/Ghre_CourseServices.cs
index 3059f973..f0e54582 100644
--- a/Tiobon.Core.Services/Ghre/Ghre_CourseServices.cs
+++ b/Tiobon.Core.Services/Ghre/Ghre_CourseServices.cs
@@ -328,7 +328,8 @@ public class Ghre_CourseServices : BaseServices<Ghre_Course, Ghre_CourseDto, Ins
 
             list.ForEach(x =>
             {
-                x.ExamPaperIds = JsonHelper.JsonToObj<List<long>>(x.ExamPaperId);
+                if (!string.IsNullOrWhiteSpace(x.ExamPaperId))
+                    x.ExamPaperIds = JsonHelper.JsonToObj<List<long>>(x.ExamPaperId);
             });
             result.result.DT_TableDataT1 = list;