Abstract: It is a hot issue in mine disaster research about the activation of faults during the process of coal mining and excavation. In order to reveal the influence of coal mining on fault activation under different fault dip conditions, Xinji No.2 mine in Huainan coalfield was taken as an example, and numerical simulation with FLAC^3D was used to systematically study the dynamic activation law of thrust faults during mining beside the faults, and to clarify the relationship among fault activation position and fault dip angle and excavated distance of working face. The results show that the fault activation is divided into three stages:Accumulation period, formation period and dynamic development period. As the working surface advances, the fault begins to activate when it is pushed to half the length of the working face, and the fault slip is the largest at the end of mining. As the fault dip angle increases, the smaller the dip angle, the earlier the fault layer begins to activate. The larger the dip angle, the larger the slip surface will be. It provides a theoretical basis and technical reference for the safe exploitation of coal resources in fault development areas.