Abstract: According to the problem of safety mining at 6415 working face under rich unconsolidated aquifer in Renlou coal mine,the methods of theoretical calculation and numerical simulation were applied to analyze the structure and seepage stability of composite water-resisting layer,and also the seepage rule of mining strata based on the material mechanics and mining seepage theory.The results showed that the composite water-resisting layer is broken after the working face advancing 45 m and the instability permeability coefficient of roof is 0.948 which closed to 1,so there is a chance of roof water inrush.The seepage velocity of coal wall in the rear of gob and the front of working face increases sharply.The water flowing fractured is mainly distributed in the tensile fractures of coal bed central part in the rear of gob and the front of working face and the state of the transfixion crack is changing with the motion of overburden.