diff --git a/src/main/java/neatlogic/module/process/workcenter/column/handler/ProcessTaskStartTimeColumn.java b/src/main/java/neatlogic/module/process/workcenter/column/handler/ProcessTaskStartTimeColumn.java
index bd9dadba9f99ab490cd02b6d4f3cf6b6f5593f12..80504cca2d08cfa544f4293950f2861ff71752fd 100755
--- a/src/main/java/neatlogic/module/process/workcenter/column/handler/ProcessTaskStartTimeColumn.java
+++ b/src/main/java/neatlogic/module/process/workcenter/column/handler/ProcessTaskStartTimeColumn.java
@@ -57,7 +57,10 @@ public class ProcessTaskStartTimeColumn extends ProcessTaskColumnBase implements
 
     @Override
     public String getSimpleValue(ProcessTaskVo processTaskVo) {
-        return sdf.format(processTaskVo.getStartTime());
+        if (processTaskVo.getStartTime() != null) {
+            return sdf.format(processTaskVo.getStartTime());
+        }
+        return null;
     }
 
     @Override