Abstract：Surface subsidence and rock movement is allowed in Mujia Hill. And 375 000 m2 continuous and gently inclined abandoned stopes were formed underground because of illegal mining. To prevent the potential danger of air shock wave resulted from sudden caving of roof and illegal mining，the abandoned stope of upside must be dilapidated. The method disposing abandoned stope is summarized，and it is proposed that the abandoned stope be disposed by roof cutting and pillar dilapidation. The 3D non-linear FEM code ANSYS is applied. The minimal roof span，the minimal cantilever roof span and roof cutting depth are studied by the 3D FEM. And then the influence of the disposing of abandoned stope on subsequent mine is analyzed. The results show that the diversification of pillar distribution necessarily results in whole change of excavating stress when the cover terrane thickness is thinner. If the minimal roof span of 102 m long or the minimal cantilever roof span of 76.5 m long and roof cutting of 8～11 m vertical deep are adopted，uncontrolled collapse of dolomite roof can be ensured. Subsequently，mining safety will not be affected by disposing abandoned stope. With sc，g known，the bigger the difference between H and covering thickness of field rock-mass is，the bigger the error calculated by the formula l=1.25H[sc /(g H)+0.001 2k]0.6 is.
