diff --git a/contest/migrations/0002_auto_20170209_0845.py b/contest/migrations/0002_auto_20170209_0845.py
new file mode 100644
index 00000000..447545f1
--- /dev/null
+++ b/contest/migrations/0002_auto_20170209_0845.py
@@ -0,0 +1,29 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.9.12 on 2017-02-09 08:45
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('contest', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='contestproblem',
+            name='_id',
+            field=models.CharField(db_index=True, default='1', max_length=24),
+            preserve_default=False,
+        ),
+        migrations.RemoveField(
+            model_name='contestproblem',
+            name='sort_index',
+        ),
+        migrations.AlterUniqueTogether(
+            name='contestproblem',
+            unique_together=set([('_id', 'contest')]),
+        ),
+    ]
diff --git a/contest/models.py b/contest/models.py
index 13da3a8f..d2fd537a 100644
--- a/contest/models.py
+++ b/contest/models.py
@@ -62,14 +62,14 @@ class Contest(models.Model):
 
 
 class ContestProblem(AbstractProblem):
+    _id = models.CharField(max_length=24, db_index=True)
     contest = models.ForeignKey(Contest)
-    # 比如A B 或者1 2 或者 a b 将按照这个排序
-    sort_index = models.CharField(max_length=30)
     # 是否已经公开了题目，防止重复公开
     is_public = models.BooleanField(default=False)
 
     class Meta:
         db_table = "contest_problem"
+        unique_together = (("_id", "contest"), )
 
 
 class ContestRank(models.Model):
diff --git a/problem/migrations/0002_problem__id.py b/problem/migrations/0002_problem__id.py
new file mode 100644
index 00000000..7c5d61dc
--- /dev/null
+++ b/problem/migrations/0002_problem__id.py
@@ -0,0 +1,21 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.9.12 on 2017-02-09 08:45
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('problem', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='problem',
+            name='_id',
+            field=models.CharField(db_index=True, default='1', max_length=24, unique=True),
+            preserve_default=False,
+        ),
+    ]
diff --git a/problem/models.py b/problem/models.py
index 54b15c89..faddb6ac 100644
--- a/problem/models.py
+++ b/problem/models.py
@@ -65,4 +65,4 @@ class AbstractProblem(models.Model):
 
 
 class Problem(AbstractProblem):
-    pass
+    _id = models.CharField(max_length=24, unique=True, db_index=True)
diff --git a/problem/serializers.py b/problem/serializers.py
index 3c1c7d81..ad21c1ad 100644
--- a/problem/serializers.py
+++ b/problem/serializers.py
@@ -33,6 +33,7 @@ class Difficulty(object):
 
 
 class CreateOrEditProblemSerializer(serializers.Serializer):
+    _id = serializers.CharField(max_length=32, allow_blank=True, allow_null=True)
     title = serializers.CharField(max_length=128)
     description = serializers.CharField()
     input_description = serializers.CharField()
diff --git a/problem/views/admin.py b/problem/views/admin.py
index 6955d554..2006841b 100644
--- a/problem/views/admin.py
+++ b/problem/views/admin.py
@@ -111,6 +111,17 @@ class ProblemAPI(APIView):
     @validate_serializer(CreateProblemSerializer)
     def post(self, request):
         data = request.data
+
+        _id = data["_id"]
+        if _id:
+            try:
+                Problem.objects.get(_id=_id)
+                return self.error("Display ID already exists")
+            except Problem.DoesNotExist:
+                pass
+        else:
+            data["_id"] = rand_str(8)
+
         if data["spj"]:
             if not data["spj_language"] or not data["spj_code"]:
                 return self.error("Invalid spj")
@@ -127,6 +138,11 @@ class ProblemAPI(APIView):
         tags = data.pop("tags")
 
         problem = Problem.objects.create(**data)
+
+        if not _id:
+            problem._id = str(problem.id)
+            problem.save()
+
         for item in tags:
             try:
                 tag = ProblemTag.objects.get(name=item)
@@ -154,12 +170,24 @@ class ProblemAPI(APIView):
     @validate_serializer(EditProblemSerializer)
     def put(self, request):
         data = request.data
+        id = data.pop("id")
         try:
-            problem = Problem.objects.get(id=data.pop("id"))
+            problem = Problem.objects.get(id=id)
             if request.user.is_admin_role():
                 problem = problem.get(created_by=request.user)
         except Problem.DoesNotExist:
             return self.error("Problem does not exist")
+
+        _id = data["_id"]
+        if _id:
+            try:
+                Problem.objects.exclude(id=id).get(_id=_id)
+                return self.error("Display ID already exists")
+            except Problem.DoesNotExist:
+                pass
+        else:
+            data["_id"] = str(id)
+
         if data["spj"]:
             if not data["spj_language"] or not data["spj_code"]:
                 return self.error("Invalid spj")