As the Chengzihe ship lock needs to cross multiple water systems，its location selection is limited by many factors，and the navigable flow conditions of its approach channel are complex.To deal with these problems，this paper carries out the technical and economic comparison and selection for the layout of the ship lock from many aspects，such as water system connection，flood control planning，navigation safety，the impact on irrigation and drainage，ship lock operation management，land acquisition and demolition，and investment.Through numerical simulation research，we set the maximum safe navigable flow conditions of 300 m3s and 120 m3s at the intersections of the approach channel with the upstream and downstream rivers，respectively.In addition，we use dredging and excavation to increase the overflow section and set up a diversion wall to adjust the main flow direction，which improves the navigable flow conditions of the approach channel.This study can provide a reference for the location selection and layout of ship locks under complex water system conditions.