Abstract: The proposed Three Gorges New Channel’s super-long water conveyance corridor runs at high head, high flow, short time and long distance. The water flow is strongly non-constant. It is very important to ensure safe operation of the ship lock. Therefore, aiming at the super-long water conveyance corridor of the last stage of the high head lock, our model numerically simulates the unsteady hydrodynamic characteristics of the water flow during valve opening. With this mathematical model, the evolution rules and influencing factors of the flow and the water level of the ship lock chamber and the valve door well are studied under different water conveyance corridor lengths and different valve opening times. The results show that longer length of the water conveyance corridor of the ship lock will increase the value and period of inertial superfall, extend the drainage time, reduce the lifting speed of lock chamber water level and decrease the reduction of the valve well water level during valve opening. Increasing the valve opening rate will reduce the drainage time, increase the lifting speed of lock chamber water level and decrease the reduction of the valve well water level during valve opening, but it can’t change the value and fluctuation period of inertial superfall. These results can be used as a reference for the design of the ultra-long discharge corridor in the last-step ship lock chamber of the Three Gorges New Channel.