Abstract: A big uplift deformation with happened only on rare occassions in the history of hydro-power projects in the world has taken place in the dam body and the surrounding mountains of Jiangya hydropower station after impoundment. In order to explore influence of water level change of the reservoir to the uplift deformation and the forecast the development of the uplift deformation,FLAG3D is applied to simulate the problem. By elaborate numerical simulation, it is shown that cycling impoundment and drainage will not obviously induce irreversible uplift deformation, and the maximum uplift deformation during the service of reservoir should approximately correspond to the maximum uplift deformation under the highest water level of the reservoir.