According to the information of terrain, water level, flow velocity and direction after and before impoundment of the Three-Gorges reservoir, we analyze the changing of the flow structure, hydraulic factors by the mathematical model for 2-dimendion flow, and channel condition, we also summarize the sediment regulation of the sharp bend and braided reach, Huanghuacheng reach, and conclude that such reaches can all be confronted with transforming of channel pattern.