The river section at the dam site of the Quanmutang Junction is an“S”sharp bend. The upstream entrance area is located on the concave bank of the narrow bend，and the downstream approach channel entrance area is at the turning point of the curved river section. The flow conditions in the entrance area and the connecting section are complicated under the influence of serious oblique flow and backflow，and it is difficult to meet the navigation requirements. The main reasons for the formation of unfavorable flow conditions in the upstream and downstream channels are studied by a model of scale 1∶100. The velocity of cross-flow and backflow is effectively reduced by comprehensive measures such as the adjustment of the upstream route，the arrangement of the dividing wall，the local dredging，and the downstream diamond-shaped pier structure. Flow conditions both in the upstream and downstream approach channels and the entrance area are greatly improved. Hydraulic indicators meet the requirements of the navigation specification，which can ensure the safety of ships.