Abstract: The study of deformation law, influence factors and failure conditions of reservoir landslide in gently under-dip slopes is carried out by physical modeling.The Xiang Jiaping landslide in the Three Gorges Reservoir region is used as a case example.Based on the similarity model, considering the factors such as water level fluctuation and rainfall(including flood season), this paper analyzes the deformation characteristics and laws of landslide with monitoring the spatiotemporal evolution of displacement, soil pressure and pore water pressure.The results show that the reservoir level rises and the front edge of the slope is continuously submerged, resulting in loosening of the soil structure and slipping in the leading edge.With decreases of reservoir water, change of displacement, soil pressure and pore water pressure were not monitored in the middle and trailing edge of the slope, but the failure of the leading edge extended backward to the middle of the slope.The independent change of reservoir water level only affects the water level of the slide bed, but when it is coupled with the bedrock fissure water of the trailing edge, the pressure of the bed can be changed.During flooding season, the soil pressure and the pore water pressure have little change, and there is no displacement deformation, because of low rainfall intensity.Under the heavy rain, the soil pressure accumulates and releases, which leads to the deformation of the middle and trailing edge of the slope.When the reservoir water level drops, the heavy rainfall would change the original stress state of the slope, and the slope would produce small deformation.Under extreme conditions, the coupling of decline of reservoir water, rainfall and the trailing edge water level can result in deformation of the slope, which makes the failure possibility of Xiang Jiaping landslide larger.The results can provide scientific basis for geological disaster prevention and mitigation in reservoir area.