Abstract: In the up stream of the Yangtze River,the construction of the hydroelectric power projects,such as Xiluedu reservoir and Xiangjiaba reserwir,changes the hydrodynamic and sediment environment of the backwater area of the Three Gorges Proj ect ( TGP).After the adjusting of the runoff-sediment by the reserwirs in the upstream,the sediment deposition and erosion in the backwater area has the corresponding changes. In this paper,based on the watersediment characteristics and fluvial process of the backwater area of the TGP,a 2D sediment mathematical model in the boundary fitting orthogonal curvilinear coordinate system is developed by the authors,then the rules of the space-time changes of the sediment deposition and erosion in the Chongqing reach is predicted in 100 years by using the model,and its effects on the harbors and navigation channels are detailedly analyaed. The Analysis of the results proves that,under the water-sediment conditions during 1960s,serious sediment deposition occurred mainly in the river sinuses,the recirculating zones and broad-shallow reach. After the construction of reservoirs,the sediment deposition wlume decreases by 82.6% in the Yangtze River and 89.7% in the Yangtze River, compared with that of 1960s,which is advantageous for the maintenance of TGP and the development of Chongqing reach.