Automatic closing device for security door

The automatic closing device for the security door comprises a door frame and a rack, a security door body is arranged in the door frame, a fixing block is arranged on one side of the front end of the door frame, the bottom end of the fixing block is rotationally connected with a closing assembly, and the closing assembly comprises a first connecting rod, a second connecting rod and a rotating rod; the tail end of the first connecting rod is rotationally connected with a second connecting rod, a rotating rod is arranged at the tail end of the second connecting rod, a gear is arranged outside the rotating rod, a mounting block is arranged outside the gear, and the rack is arranged behind the interior of the mounting block. The automatic closing device for the anti-theft door is convenient to automatically close the door during use, prevents a user from forgetting to close the door and increasing dangerous factors, is convenient to automatically and temporarily limit the anti-theft door, prevents small animals