Abstract: The depth and plane position of the goaf control the deformation characteristics of the mining slope with gently inclined layered structure and directly affect the overall stability of the mining slope. In recent years, scholars have carried out a large number of studies on the deformation of the overlying rock mass caused by underground coal mining, but the influence of goaf characteristics on the key positions of slopes has not been revealed deeply enough. The Jianshanying deformation body in the Faer Coal Mine in Guizhou Province is a typical gently-inclined layered mining slope, which has the steep upward and gentle downward, and hard upward and soft downward characteristics. The Jianshanying Deformation Body is chosen as the subject of the study in this paper. The effects of multi-layer mining and single-layer mining at different depths on the slope deformation are studied by qualitative analyses of the geological process mechanism and numerical simulation method. The width, depth and depth ratio of goaf have an important influence on the slope deformation characteristics. The results show that the multi-layer mining leads to the destruction of the slope toe and the overall collapse, which will cause the slope to produce a significant horizontal displacement, resulting in the vertical displacement of the multi-layer mining being much greater than the total thickness of the coal seam mining. The goaf crossing the slope toe, which makes the depth-to-thickness ratio decrease sharply and the mining cracks are more likely to extend to the surface, is an important factor for the destruction of the rock mass near the slope toe. When the width of the goaf increases or the multi-layer mining operation is carried out, the slope deformation increases significantly. When the depth of the goaf increases, the slope deformation value decreases, but the deformation range increases. It is beneficial to slope stability by optimizing the layout of the working face to prevent the sharp decrease of the depth-to-thickness ratio, controlling the width of the goaf, avoiding repeated mining and increasing the depth of mining, when mining in the strong terrain areas.