Abstract: Reservoir landslide is different from other mountain landslides, and its stability is obviously influenced by the fluctuation of water level. Due to its particularity and importance, the researches on the deformation characteristics and prediction of reservoir landslides have become the focus and difficult points. The fluctuation of reservoir water level will change the hydraulic boundary conditions and lead to unstable flows in the seepage field of the slope. The traditional analysis method cannot study the failure characteristics of deformation, the dynamic variation of stability and the prediction of unstable failure. So based on the numerical limit analysis, the deformation characteristics of landslides during the descending of water level and the dynamic variation law of stability are studied. The deformation characteristics of landslides are quantitatively studied through displacement-time relationship curve and its logarithmic relationship curve. The angle between the section of steep rise (acceleration section) of horizontal displacement and horizon is put forward to be the criterion for sliding prediction. It provides a new idea for understanding the failure mechanism of reservoir landslides and the improvement of prediction.