Many landslides in Three Gorges reservoir area have large deformation during the drawdown of reservoir water level every year. In this paper, based on the landslide structure and deformation characteristics of Zaozishubao in Three Gorges reservoir area, the formation mechanism and stability situation are analyzed; groundwater seepage fields are simulated by using finite element method when the reservoir water level falls, the pore water pressures are used for the analysis on limit equilibrium of landslides, the influence mechanism and laws of the drawdown rate of water level on accumulations’ stability are discussed. The analysis results showed that the landslide was formed by accumulation and transformation after sliding and bending failure of rock mass in the early stage, it is now in stable condition, but it is predicted to be in unstable state when drawdown rate of water level increases. The stability coefficient of landslide will decrease along with the reservoir water level falls, the faster water level drops, the greater stability coefficient decreases. Intensive rainfall has greater influence on the stability of landslide than the water level drawdown. The anti-slide pile reinforcement measures are proposed to improve the stability of landslide, the research methods and results have good reference value for the evaluation and treatment of the landslide.