Abstract: In order to prevent water-inrush from floor in working face and ensure the safety production of mine, take the 11141 working face of Liangbei Coal Mine as engineering background, numerical simulation was applied to study the influence of different conditions on the floor failure depth in coal mining above aquifer, such as advanced distance of working face, burial depth, thickness of coal seam, fault and fault location. The study results showed that: the greater the advanced distance of working face, the greater the floor failure depth, but after a certain distance, the floor failure depth remain unchanged and tend to stable; the greater the burial depth, the greater the floor failure depth, but the increase speed will decrease; the greater the thickness of coal seam, only increase the damage range of floor, there is no influence to the floor failure depth; the floor failure depth is greater when there is a fault, it will be more severely to the impact of the floor failure depth when the fault is located within the range of first weighting than which is located within the range of periodic weighting. The research conclusion can give a reference to the safety mining of working face in coal mining above aquifer.