Abstract: Based on the condition of the nearly flat coal seam of Bulianta Coal Mine, we research different mining height that is main influencing factor of overlying rock movement and damage by the numerical simulation program FLAC^3D and respectively establish quantitative relationship between different mining height and surface movement, overlying rock damage, tensile areas, which can forecast damage extent of the overlying rock in large mining height in the mined-out area, and we can take measures to prevent sand inrush and water inrush in the working face and protect plants on the surface.