Abstract: Coal mining underground will cause the surrounding rock to move, causing changes in surface morphology, indirectly causing erosion on the slope. Based on the mining conditions and soil erosion characteristics of the Dafosi coal mine, the effects of the thickness of the loess layer on the slope morphology and erosion of the coal mining subsidence area are studied with the thickness of the loess layer and slope type as variables. Using FLAC 3D numerical simulation software to simulate the surface deformation caused by coal mining, the results show that underground coal mining will inevitably lead to slope increase, slope length decrease, slope erosion modulus and runoff modulus increase. The thickness of loess layer greater than 100m can effectively control the slope increase, the slope length decrease, the slope erosion modulus and the runoff modulus increase. The thickness of the loess layer is increased, and the natural slope types corresponding to the increase of slope erosion from large to small are: linear slope, convex slope, concave slope, mixed slope and increasing the thickness of the loess layer is more effective in controlling the influence of the slope morphology and slope erosion.