Abstract: In the inter-basin water transfer project, the hydraulic junction in the branch mouth of a tidal river is often located near the main river and keeps an open layout due to the restriction of land areas. The flow condition at the branch mouth is restrained by asymmetrical tidal current, which makes it difficult to coordinate the diversion, drainage and navigation functions. Taking Jiepai Hydraulic Junction of Xinmenghe Extension-Drainage Project as an example, by combining physical model with mathematical model test, we obtain the overall flow condition, reveal the formation mechanism of bad flow pattern, and put forward the overall layout principles of the junction. The results show that the flow condition at the branch mouth is significantly influenced by the fluctuation tide, which leads to the bank head protruding current and the oblique flow at the inlet of the pumping station, the sluice gate and the entrance of the lock approach channel. The boundary of the inner river is fixed, and the sluice is located in the middle of the inner river, which leads to a smooth flow condition. The overall layout of the project follows the principles: the branch and the main river are arranged at sharp angles, and the exact angle value depends on the duration of fluctuating tide to coordinate the diversion function; the bank head between the branch and the main river is arranged in a two-layer cascade shape, the lower cascade is at an acute angle, and the upper cascade is at blunt angles, to coordinate the drainage function; the sluice is arranged in the middle of the branch, the ship lock is arranged at the side always with smooth flow condition, and the pump station is arranged at the other side, to coordinate the navigation function. The junction should be constructed far away from the tidal river if possible, so that the pump station and approach channel are sheltered by the shoreline and bad flow pattern is reduced, to coordinate the whole functions. The junction should be constructed far away from the tidal river if possible, so that the pump station and approach channel are sheltered by the shoreline and the bad flow pattern is reduced, to coordinate the whole functions.