In the improved index system, underground coal mining is chosen as the research object. Such conditions as natural environment, mining and coal mine occurrence constitute the constrained layer and eleven impact factors, such as terrain slope, land exploitation planning and coal seam thickness, constitute the index layer. Delphi and analytic hierarchy process (AHP) methods and YAAHP(V6.0)software are employed to determine the weight of each index. The weight comparison shows that in order of decreasing weight, the three compared conditions are the coal mine occurrence, mining and natural environment; the coal mine occurrence conditions are the coal seam thickness, dip angle of coal seam and ratio of crack depth; the mining conditions are the roof management method, coal mining technology and mining degree; and the natural environment conditions are the land exploitation planning, effective thickness of soil layer, precipitation, soil texture and slope of the terrain. The improved index system lays a foundation for determining the modified coefficient of the reclamation cost for the land destroyed by underground coal mining.