diff --git a/submission/migrations/0008_auto_20151208_2106.py b/submission/migrations/0008_auto_20151208_2106.py
new file mode 100644
index 00000000..b3a85763
--- /dev/null
+++ b/submission/migrations/0008_auto_20151208_2106.py
@@ -0,0 +1,25 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.9 on 2015-12-08 13:06
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('submission', '0007_auto_20151207_1645'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='submission',
+            name='judge_end_time',
+            field=models.BigIntegerField(blank=True, null=True),
+        ),
+        migrations.AlterField(
+            model_name='submission',
+            name='judge_start_time',
+            field=models.BigIntegerField(blank=True, null=True),
+        ),
+    ]
diff --git a/submission/models.py b/submission/models.py
index a0db4b3d..fc1a0708 100644
--- a/submission/models.py
+++ b/submission/models.py
@@ -9,9 +9,9 @@ class Submission(models.Model):
     user_id = models.IntegerField(db_index=True)
     create_time = models.DateTimeField(auto_now_add=True)
     # 判题开始时间
-    judge_start_time = models.IntegerField(blank=True, null=True)
+    judge_start_time = models.BigIntegerField(blank=True, null=True)
     # 判题结束时间
-    judge_end_time = models.IntegerField(blank=True, null=True)
+    judge_end_time = models.BigIntegerField(blank=True, null=True)
     result = models.IntegerField(default=result["waiting"])
     language = models.IntegerField()
     code = models.TextField()
@@ -28,3 +28,6 @@ class Submission(models.Model):
 
     class Meta:
         db_table = "submission"
+
+    def __unicode__(self):
+        return self.id