Abstract: To study the law of surface movement and deformation in downward mining under complex landform conditions, combined with the engineering geological conditions of a coal mine in Shanxi Province, a combination method of theoretical analysis and FLAC3D numerical simulation is used to construct a three-dimensional model with complex landforms. The characteristics of the movement and deformation of the ground surface and the instability and failure mechanism of the surface slope under the 8# coal and 11# coal repeated downward mining operation. The results show that due to the small overburden thickness of the 8# coal seam, after the mining of the 8# coal seam, the fracture zone in some areas above the goaf reaches the surface directly; the depth of the failure zone of the 8# coal seam floor is up to 16.08 m, which has a certain effect on the stability of the 11# coal roof , but the 11# coal mining can still form a stable roof; the maximum surface subsidence values under the 8# coal and the 11# mining are 1.331 m and 1.626 m, respectively, and the surface subsidence area presents a near ellipse with the goaf as the center, the deformation range of ground movement under repeated mining changes little; the surface movement deformation is affected by the topography, and the surface subsidence range and horizontal displacement in the steep slope area significantly increase; the shear stress concentration occurs at the foot of the surface slope, and the rear edge of the slope body is subjected to tensile stress. Under the action of rainfall and vibration, the slope is prone to damage and forms the geological disaster.