Aiming at the problem which the post - procession of FLAC3D could not intuitively and quantificationally show failure state of rock mass,the rock stability of four continuous mining steps in a mine was simulated with FLAC3D based on Mohr circle theory. The studied results showed that Mohr circle is intuitionistic,convenient and effective in reflecting the stability of rock mass. The study has solved commendably the difficult problem which the stability state of rock mass can’t be showed by Mohr - Coulomb criterion in FLAC3D.