Abstract: According to the sand conservation and the characteristics of flow and sediment transports of lake,a two-dimensional unsteady flow and nonuniform sediment model is established.The paper compares the two transformation modes of wash load and bed material load,by calculating flow and sediment transports and riverbed deformation of Dongting Lake.Based on the above,the modes of sediment deposit and moving water-and-sand boundary,especially for wash load,are put forward.The calculated results prove that the numberical mode of sediment deposit for the Dongting Lake possesses better sability and higher simulant precision.It is showed that the established deposited model for the lake has good performance and popularizing prospect.