Abstract: Taking geological data of F₅ reverse fault in a coal mine as the background, we use FLAC^3D software to study the fault zone stress evolution and faults activation laws when the upper and lower plates of the working face are orderly mined to reveal the relationship between inverse fault activation and throw in mining period. Study shows that the normal stress of fault throw and fault belt is proportional to change of stress and displacement of the two plates in the lower coal seam mining, that is, with the increase of fault throw, the displacement amount of two plates and the normal stress are reduced; the smaller of fault throw is, the higher of activation level is, and the more risk of water inrush is; so, the mining of two plates shows different patterns, needs to be distinguished and prevention measures in practice.