Zhenggang deposit talus at Gushui Hydropower Station is in a stable state at present. However, it may become unstable under conditions of rain or earthquakes, which may lead to landslides and even threaten the safety of cavern exits downstream. In order to solve this problem, a typical geological profile was chosen for geological characteristic analysis. Then, a granular discrete element model was built for numerical simulation of landslide reactivation in different cases. The results show that cracks easily occur near the position where the dip angle of the slip surface increases sharply or a fault develops, which also affects the initial landslide position. When the water pressure of three meters is loaded on the slip surface, the deposit talus starts to creep, and when the water pressure reaches five meters, a third-stage landslide may become active aqain. When the seismic strength reaches 0.3g, the deposit talus on the first platform begins to slide, and a third-stage landslide is generated.