Abstract: According to the quantity conservation principle of any grain sediment during the sediment transportation course,this paper,based on the former research,builds a one-dimensional unsteady sediment-laden flow equation.By introducing the concepts of particle diameter and a balance state of scouring and depositing,this paper sets up a formula about particle diameter of scouring and depositing material and brings forward an integrate method for calculating the suspended load and the bed load exchanging.This method is introduced to one-dimensional expanded sediment numerical model.It is verified by the typical flood in 1977 and the scouring series from the end of flood period in 1999 to its the beginning in 2002.The result shows that this method may preferably simulate the exchanging course between suspended load and bed load.This method gets over the limitation of the former one based on the transferring capacity of grouping sediment,and improves the calculation of the non-uniform sediment in theory and may be more perfectian application.