The channel in the downstream section of the Qianjiang Datengxia hydro-junction has complex and unfavorable flow patterns，frequent maritime incidents，and natural channel attributes in dry seasons，and thus the scale of the channel needs to be greatly improved. Considering these problems，two channel lines are arranged according to the principles of straightening the channel as much as possible and increasing the bending radius. Using the model of navigation flow conditions for experiments，we analyze the complex navigation-hampering flow conditions of the continuous beach group and obtain the optimization idea of eliminating the deflecting flow point，smoothing the flow edge，and effectively increasing the cross-sectional area of the flow for regulating navigation-hampering shoals. On the basis of the preliminary design scheme No.2，an optimization scheme is proposed to increase the radius of the curved top section and its upstream and downstream reef-blasting range and clear the left side beach and the right high beach. The verification by the physical model and ship model indicates that the optimized design scheme can effectively improve the flow patterns and navigation conditions.