Abstract: Taking Xinglongzhuang Coal Mine as the engineering background, FLAC^3D numerical simulation is used to study the mining stress and activation laws under the condition of different fault drop. The research shows that the stress concentration degree of the surrounding rock of the roof and floor and the supporting pressure of the working face increase with the increase of the drop in the footwall mining, and the mining on the hanging wall shows the opposite law. When the footwall face is mined and the working face is 30 m away from the fault, the ratio of shear stress to normal stress is the biggest, at this time, the fault is easy to be activated and unstable. When the fault drop is 8 m, the ratio of shear stress to normal stress is the maximum; when the fault drop is 4 m, the ratio is minimum. For the high rock layer, the maximum ratio of shear stress to normal stress increases with the fall of the fault. The variation trend of shear stress and normal stress ratio is consistent with the change of fault drop. When the upper and lower face is mined, roof subsidence increased gradually with the increase of the fault drop.