Abstract: his paper analyzed mutual influence of fault activation and mining by numerical simulation. When tangential stress increased to shear strength， fault reached critical state of instability， minor disturbing would result in fault activation and release energy at this time. Coulomb stress increment Δσm was main reason of fault activation and probability of fault activation was proportional to Δσm. When mining face advancing to fault from fault＇s hanging wall， normal and tangential stress on fault plane both increased. When mining face advancing to fault from fault＇s footwall， normal stress decreased and tangential stress increased， this resulted in fault activation. One side， mining might change stress field of fault and result in fault activation. On the other side， fault activation might influence mining.