In view of the influence of the gate opening mode on the flow characteristics and navigation flow conditions of the downstream approach channel entrance area of the junction，taking the second ship lock of Jinweizhou junction in the Xiangjiang River as an example，we build a two-dimensional flow mathematical model that can better simulate the complex river boundary conditions.On the basis of fully understanding the flow conditions of the downstream approach channel entrance area under the conventional design discharge and sluice opening mode，we carry out a combination test study of multiple sluice opening and discharge modes.The results show that the flow at the entrance area of the downstream approach channel of the second ship lock is greatly affected by the operation mode of the junction.The rational arrangement of the side hole (22# sluice hole) can increase the energy loss of the reflux flow at the entrance area，thereby reducing the reflux flow at the entrance area，and at the same time，the longitudinal and transverse flows can also meet the code requirements.To ensure the safety of ship navigation，it is suggested that the project should adopt the mode of the conventional gate opening and side hole improving flow as far as possible when discharging flood.