The proposed Zhangkan Navigation-power junction in the Minjiang River is located on the S-shaped curved channel.The flow conditions in the downstream entrance area of the ship lock are difficult to meet the navigational standards due to the influence of the curved channel and complex riverbed topography.In view of the flow conditions of the project,a two-dimensional numerical simulation method of water flow is adopted.On the basis of fully utilizing the original topography of the downstream entrance area,three optimization schemes are proposed by changing the shape of the guidance wall of the approach channel,extending the guidance wall of the approach channel and deflecting to the left bank,and adding diversion piers.The results show that the arrangement scheme of adopting R=125 m curved guidance wall and one diversion pier can not only effectively reduce the cross-flow and back-flow velocity in the entrance area,but also destroy the formation conditions of back-flow in the connecting area through the gap between the diversion pier and the guidance wall,thus improving the condition of back-flow caused by the curved guidance wall in the connecting area under the high flow rate.The optimized downstream flow conditions in the entrance area and the connecting area meet the navigational standards,and the research results can provide references for similar projects.