Based on deformation survey and numerical analysis, the process of slope deformation was studied during the slope cutting and under rainfall conditions. The slope stability factor of each excavation step also was calculated, and then the landslide deformation mechanism was investigated. The result shows that the leading edge of the slope occur deformation firstly because of resistance against sliding decreased, which entice develop tension cracks at the trailing edge of the slope. Rainwater infiltrate into the slope body along the cracks under the condition of rain, which makes bulk density of rock and soil increased, and its shear strength reduced, so that the deep sliding failure is emerged. The analysis shows that, as to soil slope of Dakeng village, excavation and artificial rainfall is the main factors of deep sliding. The structural of rock and soil become loose after deep sliding that induce shallow landslides easily at the leading edge of the slope under rainfall conditions.