Drainage outlet project is a special river-facing project because it continuously injects water into the channel,and the scientific and reasonable construction of the project is very important to ensure the safety of the channel and navigation.Aiming at the change of navigation conditions after the renovation of the drainage outlet of Tangwang sewage treatment plant in the downstream approach channel area of Shiqiao lock,we study the location and layout of the drainage outlet project,analyze the navigation conditions of the channel using the model established by MIKE21 software,and propose some suggestions for the construction of the drainage outlet project.The results show that the construction of the drainage outlet project will bring adverse effects on navigation conditions of the lower approach channel of the ship lock.By optimizing the layout,reducing the elevation of the drainage outlet and increasing the diameter of the drainage outlet,the adverse cross-flow velocity can be effectively reduced to satisfy the requirements of the standard.