On May 10, 2007, the Muzhuping landslide moved into Modao-he River caused by impoundment and early rainfall, which is a first landslide hazard in the Shuibuya Reservoir. Using ABAQUS software to analysis the mechanism of deformation with considering the coupling Seepage-stress, and by according to residual thrust method, some predictions of the slope stability were performed with considering to fluctuation of the reservoir water. The numerical results show that the initial impoundment and rapid declining of reservoir water level are most dangerous for a reservoir.