Abstract: To study the mechanics mechanism of water inrush in containing hidden faults of mining-induced seam floor, we established a mechanical model according to the actual characteristics of containing hidden faults occurrence in floor. Using the theory of fracture mechanics, we researched the formation process of floor water-inrush passage under the joint action of mining-induced stress and confined water in the process of working face advancing, obtained the mechanical criterion for the water inrush of hidden fault, analyzed the main factors. The results show that the critical water pressure q is mainly affected by the length of the buried fault a, the dip angle β, the support pressure Q, the thickness of the h and other factors. But the critical water pressure is the essential condition of the water inrush; when the branch crack length reaches a certain value and the effective thickness of the water layer is not enough to resist the pressure of the mining-induced stress and confined water, it can satisfy the sufficient conditions of water inrush. According to the engineering geological conditions of actual working face, we use numerical simulation method to analyze floor stress and seepage condition in the process of floor damage. The theoretical analysis results are verified by numerical simulation method.