Abstract: It is mainly discussed that the minimum safe thickness of the stope roof and the ground subsidence deformation during mine excavation.The concrete method is deducing the theoretical calculation formula of minimum thickness of the stope roof according to the bending and shearing structural mechanics model respectively so as to gain the minimum safe thickness; A detailed engineering geological 3d model for mining concessions is built by using Auto CAD，and next a numerical calculation model is established by using ANSYS finite element software，following by importing it to numerical simulation software FLAC3D for calculation.By this method，the whole process of mine excavation can be simulated.Finally，the ground subsidence deformation obtained by simulation satisfies the specification requirements.

Key words: Mine excavation, Numerical simulation, Thickness of the roof, Stability