Abstract: A numerical model to simulate sediment transportation and riverbed variation in river networks is presented.Flow simulation is based on commonly used the gradation method,in which the matrix formed junction equations are divided by subarea groups.For simulation of sediment transportation process,several methods are compared to describe sediment diversion at the junction nodes,together with analysis of their advantage and suitable situation in application.By means of the sediment diversion methods,sediment transport equations can also be solved by the gradation method with the divided junctions groups.The technique to handle junction nodes in which water and sediment deposition can be stored is also discussed for applying to flood retarding basin.Finally,with the data of Dujiatai retarding basin in Hanjiang River,the validity of the model is checked,and the result shows that the model can be applied in wide practice and is worth recommending.