This study investigated the change hydrodynamic characteristics at the confluence reach in BaiShi Reservoir area in the Daling River with different factors, based on model testing. The results show that the water depth and flow area increase along the channel, and the flow velocity in the mainstream and tributaries upstream of the confluence zone increases along the channel as well, while the flow velocity downstream of the confluence zone decreases significantly along the channel. The backflow region occurs in the tributaries downstream of the confluence zone, and its range increases with the confluence ratio. When the water level upstream of the dam increases, the absolute value of the velocity and its change rate along the channel decrease in the confluence zone, while the degree of curvature of the main stream line and the backflow region range increase.