The second-line ship lock of Jinweizhou Junction in Xiangjiang is an upgrade and reconstruction project. There is no choice of location and axis. The navigational flow conditions in the entrance area of the downstream approach channel can only be improved by optimizing the opening method or constructing a diversion pier. Using 1:100 fixed-bed normal river physics model test，on the basis of fully understanding the water flow conditions of the downstream approach channel entrance area of the conventional gate discharge method，through a combination of multiple-gate discharge methods and diversion pier layout optimization experiments such as number，spacing，angle，etc.，we propose the conventional way of opening gate + side hole supplementary discharge，or the arrangement of three diversion piers with a single pier length of 20 m，a direction parallel to the route，and a spacing of 20 m. Both can be opened to the traffic flow increased to a flood in 2 years.