The Muyubao landslide is an extremely large ancient landslide in the Three Gorges Reservoir area. It has been continuously deformed for a long time, which poses a serious threat to the navigation channel of the Three Gorges. In this paper, through the automatic GPS surface displacement, deep displacement, groundwater level and rainfall monitoring of Muyubao landslide in recent two years, the deformation characteristics and deformation mechanism of the landslide are studied, and the stability change characteristics in a complete hydrological cycle are calculated by using finite element software. The results show that: (1) the deformation of the front part of Muyubao landslide is larger than that of the back part of the landslide. The deformation mainly occurs in the period of reservoir water level rise and high water level operation, and also increases greatly in the stage of rapid decline of reservoir water level. (2) The permeability coefficient of rock and soil is larger when the front edge of landslide mass is between 159 and 175m, and the permeability coefficient of rock and soil mass between 159 and 145m is relatively small. (3) The rise of reservoir water level and high water level are the main factors affecting the deformation of landslide, and the rapid decline of reservoir water level is the secondary factor of landslide deformation, while the influence of atmospheric rainfall on deformation is not obvious, which is basically stable.