The ship lock water gallery is the main equipment for completing the lock chamber water discharge. To meet the needs of ship locks,the Gezhouba Shiplock has a maintenance flat door in the water conveyance corridor.The drop of it can block water temporarily,then through pumping and drainage,we can realize the dry maintenance of the lock chamber or valve well.Therefore，it is extremely important to check the water-stopping effect after the flat door is lowered，which is directly related to the lockout time of the shiplock.Through the investigation of the water leakage problem after the flat door of Gezhouba ship lock waterway is overhauled,we analyze factors causing water leakage,and propose suggestions and measures for the door drop and process improvement,so as to provide reference for the improvement of the dropping,placement and inspection process.