Baishiyao hydropower station is located on the middle reaches of the Beijiang river,downstream near Feilaixia hub,and the flow conditions of the reaches under the dam are very complicated by the influence of backwater.So the physical model is used to study it,and the model is proven to satisfy the similarity requirements through verification.Fluvial process analysis about the reaches is carried out.According to the results of fixed bed model test,a preliminary analysis of waterway stability is made from the regulation line of waterway and flow dynamic axis,the angle between channel axis and the stream thread,change of flow velocity between before and after channel improvement,gradient,as well as transportability of sediments.The amount of dredge-cut siltation is got based on the movable-bed model test.The suggestion is offered to keep the waterway stable.