To analyze the impact of unsteady flow on downstream navigation during sudden load shedding and turbine cutting operation of power plant units,this paper takes Xiangjiaba hydropower station as the research object,Establishes a 1:100 normal physical model,simulates the turbine cutting conditions of Xiangjiaba hydropower station units,analyzes the changes in water level and flow velocity in the downstream reach caused by unsteady flow under different turbine cutting numbers of 8 units.At the same time,combines with self-propelled ship model tests to study the impact on safe navigation of ships.The results show that when the power plant units cut off 1-8 units respectively,under the condition of rapid water replenishment,the maximum hourly variation of downstream water level is 0.89 m/h,which does not exceed the allowable value in the power plant operation and scheduling regulations.The water level changes caused by unsteady flow mainly occur in the river section above Tongzilin,while the flow velocity changes mainly occur in the river section above Heshangyan.The flow conditions meet the requirements of ship navigation.The research results can provide technical support for the dispatch and operation of power plants,downstream channel maintenance,and ship navigation.