diff --git a/oj/urls.py b/oj/urls.py
index 909d6bb..ba7c997 100644
--- a/oj/urls.py
+++ b/oj/urls.py
@@ -14,7 +14,8 @@ from group.views import (GroupAdminAPIView, GroupMemberAdminAPIView,
 from admin.views import AdminTemplateView
 
 from problem.views import TestCaseUploadAPIView, ProblemTagAdminAPIView, ProblemAdminAPIView
-from submission.views import SubmissionAPIView
+from submission.views import SubmissionAPIView, SubmissionAdminAPIView
+
 
 urlpatterns = [
     url(r'^install/$', "install.views.install"),
@@ -57,5 +58,6 @@ urlpatterns = [
     url(r'^api/admin/join_group_request/$', JoinGroupRequestAdminAPIView.as_view(),
         name="join_group_request_admin_api"),
     url(r'^api/submission/$', SubmissionAPIView.as_view(), name="submission_api"),
+    url(r'^api/admin/submission/$', SubmissionAdminAPIView.as_view(), name="submission_admin_api_view"),
 
 ]
diff --git a/problem/serizalizers.py b/problem/serizalizers.py
index d53b2bb..1fb61cc 100644
--- a/problem/serizalizers.py
+++ b/problem/serizalizers.py
@@ -30,7 +30,7 @@ class CreateProblemSerializer(serializers.Serializer):
     memory_limit = serializers.IntegerField()
     difficulty = serializers.IntegerField()
     tags = serializers.ListField(child=serializers.CharField(max_length=10))
-    hint = serializers.CharField(max_length=3000, required=False, default=None)
+    hint = serializers.CharField(max_length=3000, allow_blank=True)
 
 
 class ProblemTagSerializer(serializers.ModelSerializer):
@@ -66,7 +66,7 @@ class EditProblemSerializer(serializers.Serializer):
     difficulty = serializers.IntegerField()
     tags = serializers.ListField(child=serializers.CharField(max_length=20))
     samples = ProblemSampleSerializer()
-    hint = serializers.CharField(max_length=10000)
+    hint = serializers.CharField(max_length=3000, allow_blank=True)
     visible = serializers.BooleanField()
 
 
diff --git a/problem/views.py b/problem/views.py
index 1d1702d..4a6e2c6 100644
--- a/problem/views.py
+++ b/problem/views.py
@@ -22,7 +22,7 @@ from .models import Problem, ProblemTag
 
 def problem_page(request, problem_id):
     try:
-        problem = Problem.objects.get(id=problem_id)
+        problem = Problem.objects.get(id=problem_id, visible=True)
     except Problem.DoesNotExist:
         return error_page(request, u"题目不存在")
     return render(request, "oj/problem/problem.html", {"problem": problem, "samples": json.loads(problem.samples)})
@@ -122,7 +122,7 @@ class ProblemAdminAPIView(APIView):
                 return success_response(ProblemSerializer(problem).data)
             except Problem.DoesNotExist:
                 return error_response(u"题目不存在")
-        problem = Problem.objects.all().order_by("-last_update_time")
+        problem = Problem.objects.all().order_by("-create_time")
         visible = request.GET.get("visible", None)
         if visible:
             problem = problem.filter(visible=(visible == "true"))
@@ -217,7 +217,7 @@ class TestCaseUploadAPIView(APIView):
 
 def problem_list_page(request, page=1):
     # 正常情况
-    problems = Problem.objects.all()
+    problems = Problem.objects.filter(visible=True)
 
     # 搜索的情况
     keyword = request.GET.get("keyword", None)