Abstract:The selection of model sediment is the key factor in the design of movable bed model.In view of high variable rate of Poyang Lake model and the fine sand into lake,the light model sand should be adopted in movable bed model.Combined with the flume starting velocity test,the size scale of model sand was preliminarily designed by using the reasearch results of the similarity of sediment movement condition.The suitable model sand was selected.The incipient velocity formula of plastic model sand was proposed to estimate incipient velocity of palstic sediment,combined with several domestic lightweight formula of incipient velocity.improving the simulation accuracy of movable bed model test.