Xijin hydro-junction project is situated in a C-shaped curved section of the river with towering mountains on both sides.Due to the safety and operation conditions of the built facilities,it is difficult to select the location and plane layout of the second-line ship lock.On the basis of summarizing the construction experience of similar projects,according to the characteristics of Xijin hydro-junction project,this paper puts forward the principles of lock location selection.The principles take into account factors such as the impact on existing hub facilities in terms of safety and functionality,navigable water flow conditions at the lock site,project area and demolition requirements,construction scheme feasibility,convenience of operation and management,excavation volume,and project investment.The combination of qualitative analysis and quantitative calculation method is used to compare and select an optimal position for the second-line ship lock.Combined with the physical model test,the length of upstream and downstream barrier is optimized to improve the navigable flow conditions in the entrance area of the upstream and downstream approach channel.Field operation tests confirm that the proposed lock's passage capacity meets design requirements and achieve efficient navigation goals.The principle and research method of lock-location proposed can provide reference for the general arrangement of locks in similar high head reservoir area.