Abstract: Large and medium-sized faults of water-containing and water-conducting could produce great damage for coal mine safety production, generally it used the method of setting waterproof pillars to control. In the condition of mining, faults could produce different degree of activation which caused certain influence to the safety of waterproof coal pillars. By analyzing the geological and hydrogeological conditions of F₁₀ fault in Xinji NO.1 Mine, it used the numerical simulation software Flac^3D to simulate the displacement and stress distribution of the fault zone and two strata when working face mining along and against faults, then it analyzed the characteristic of movement and destruction, and its effect on waterproof coal pillars. The simulation results showed that when the coal seam excavation of top wall was 15 m away from the fault, the stress and displacement on both sides of the fault changed differently, existing "activation" trend, which had lesser influence on the waterproof coal pillars which would not affect its safety. When the coal seam excavation of footwall was 25 m away from the fault, the fault changed obviously, the range of plastic zone expanded up to the strata against the fault, had the obvious phenomenon of "activation", which had greater effect on the waterproof coal pillars.