Abstract: In order to study the influence of basement inclination on the stability of the dump slope under rainfall conditions, according to the actual situation of Antaibao Open-pit Coal Mine, FLAC^3D software was used to simulate the slope of the dump under the same rain intensity and different base inclination angles. The results show that in the early stage of rainfall, the saturation of the surface layer of the dump slope first grows rapidly and tends to the stable value of unsaturation, and when the rainfall infiltrates to the junction of the weak layer and bedrock, the rainwater accumulates at the slope angle under the action of gravity and leads to shear failure at the slope angle. With the increase of the basement inclination, the time lag effect occurred in each monitoring point when it reached saturation or steady state, and the displacement and strain increment were positively correlated with the substrate inclination.