Abstract: According to the requirement of mass and energy continuity of water and sediment and the analysis the water sediment model of single reach,a numerical model for calculation og the normal river system is established in this article,and tested by the observed data of the the Jingjiang River and the Dongt ing Lake in 1997. The result shows that the computed data and observed fits well,which indicates that it is suitable to sum the complex boundary of the Jingjiang-Dongt ing Lake and is applicable.