The water level fluctuation in the upper approach channel will be caused during the filling process of the ship locks, and the formation of undesirable flow regimes such as oblique currents, backflows, and separation eddies will adversely affect the safety of ship navigation and berthing.Relying on Baishiyao hub project, this paper adopts RNG k-ε turbulence model to analyze the water level, wave speed and other hydraulic characteristics under different conditions for the non-constant flow problem caused by staggered operation in the upper approach channel of double-line ship lock.The results show that the staggered operation of double-line ship lock will cause the corresponding water level fluctuation amplitude to be reduced, and the water level change process is more complicated during the filling period of the lock.Surface eddies appear in a certain range near the intake.Even cascading funnel whirlpools occur, affecting the water intake and lock chamber water delivery conditions, as well as the valve working condition.By assessing the adverse effects on the navigation and mooring of vessels, it is concluded that simultaneous water filling in the double-line ship lock should be avoided.The flow conditions in the approach channel and the flow patterns at the intake should be strengthened in terms of prototype observation.Based on the results of the prototype observation, the opening mode and time of the water filling valves in the double-line ship lock should be adjusted, and the joint dispatching of the double-line ship lock should be strengthened to ensure the safety of vessels passing through the lock.The research results provide a scientific basis for improving the capacity of the ship lock.