Abstract: A long river model, whose total length is about 800m, is used to simulate the varing backwater zone of the Three Gorges Project, covering 200km long of natural river reaches of the Yangtze River and Jialing River. The model is designed based on the total load similarity theory developed by first author. Verification tests show that the model has a basic similarity agreement with the prototype in the aspects of resistance characteristics,flow conditions and laws governing scouring and deposition. By using this model, a series of tests with normal reservoir elevations at 175m, 180m, and 156m with reservoir operation for 80 years and 30 years have been conducted to study the laws governing scouring and deposition in the varying backwater zone, the siltation configuration in channels and harbours for the feasibility studies of the Three Gorges Project.