diff --git a/account/serializers.py b/account/serializers.py
index 945e0967..d3466776 100644
--- a/account/serializers.py
+++ b/account/serializers.py
@@ -40,8 +40,7 @@ class GenerateUserSerializer(serializers.Serializer):
     suffix = serializers.CharField(max_length=16, allow_blank=True)
     number_from = serializers.IntegerField()
     number_to = serializers.IntegerField()
-    default_email = serializers.CharField(max_length=64)
-    password_length = serializers.IntegerField(required=False, max_value=16)
+    password_length = serializers.IntegerField(max_value=16, default=8)
 
 
 class ImportUserSeralizer(serializers.Serializer):
diff --git a/account/tests.py b/account/tests.py
index bf537273..43a09fe2 100644
--- a/account/tests.py
+++ b/account/tests.py
@@ -1,4 +1,5 @@
 import time
+
 from unittest import mock
 from datetime import timedelta
 from copy import deepcopy
@@ -610,6 +611,3 @@ class GenerateUserAPITest(APITestCase):
         resp = self.client.post(self.url, data=self.data)
         self.assertSuccess(resp)
         mock_workbook.assert_called()
-        data = resp.data["data"]
-        self.assertEqual(data["created_count"], 6)
-        self.assertEqual(data["get_count"], 0)
diff --git a/account/views/admin.py b/account/views/admin.py
index 3e8fb471..b1ef6889 100644
--- a/account/views/admin.py
+++ b/account/views/admin.py
@@ -173,9 +173,6 @@ class GenerateUserAPI(APIView):
         if data["number_from"] > data["number_to"]:
             return self.error("Start number must be lower than end number")
 
-        password_length = data.get("password_length", 8)
-        default_email = data.get("default_email")
-
         file_id = rand_str(8)
         filename = f"/tmp/{file_id}.xlsx"
         workbook = xlsxwriter.Workbook(filename)
@@ -184,26 +181,27 @@ class GenerateUserAPI(APIView):
         worksheet.write("A1", "Username")
         worksheet.write("B1", "Password")
         i = 1
-        created_count = 0
-        get_count = 0
+
+        user_list = []
         for number in range(data["number_from"], data["number_to"] + 1):
-            username = f"{data['prefix']}{number}{data['suffix']}"
-            password = rand_str(password_length)
-            user, created = User.objects.get_or_create(username=username)
-            user.email = default_email
-            user.set_password(password)
-            user.save()
-            if created:
-                UserProfile.objects.create(user=user)
-                created_count += 1
-            else:
-                get_count += 1
-            worksheet.write_string(i, 0, username)
-            worksheet.write_string(i, 1, password)
-            i += 1
-        workbook.close()
-        return self.success({
-            "file_id": file_id,
-            "created_count": created_count,
-            "get_count": get_count
-        })
+            raw_password = rand_str(data["password_length"])
+            user = User(username=f"{data['prefix']}{number}{data['suffix']}", password=make_password(raw_password))
+            user.raw_password = raw_password
+            user_list.append(user)
+
+        try:
+            with transaction.atomic():
+
+                ret = User.objects.bulk_create(user_list)
+                UserProfile.objects.bulk_create([UserProfile(user=user) for user in ret])
+                for item in user_list:
+                    worksheet.write_string(i, 0, item.username)
+                    worksheet.write_string(i, 1, item.raw_password)
+                    i += 1
+                workbook.close()
+                return self.success({"file_id": file_id})
+        except IntegrityError as e:
+            # Extract detail from exception message
+            #    duplicate key value violates unique constraint "user_username_key"
+            #    DETAIL:  Key (username)=(root11) already exists.
+            return self.error(str(e).split("\n")[1])
diff --git a/oj/dev_settings.py b/oj/dev_settings.py
index 724a5dc4..5d9cb9e5 100644
--- a/oj/dev_settings.py
+++ b/oj/dev_settings.py
@@ -7,7 +7,7 @@ DATABASES = {
     'default': {
         'ENGINE': 'django.db.backends.postgresql_psycopg2',
         'HOST': '127.0.0.1',
-        'PORT': 5433,
+        'PORT': 5432,
         'NAME': "onlinejudge",
         'USER': "onlinejudge",
         'PASSWORD': 'onlinejudge'