Abstract: Taking F₅ reverse fault of 10605 working face in Yangcun Coal Mine as the research object, the three-dimensional finite difference numerical software FLAC^3D was adopted to study the effect of fault dip on the activation of the reverse fault and reveal the laws of fault dip angle on the activation of the reverse fault. The results show that when the coal seam is mined in the footwall of reverse fault, with the decreasing of fault dip, the stress on the fault zone is greater. The smaller of the fault dip, the greater of the displacement of the upper and down level of the fault changes. The extent and destruction degree of pore pressure in the fault zone decrease with the increase of the dip angle of the fault. The above achievements can indicate that reverse faults with low dip angles are more easily activated to induce water inrush in coal floor and wider waterproof coal pillars are needed.