Abstract: In order to solve the problem of large deformation and serious damage of mine roadway in the underline coal seam of contiguous coal seams, which had an effect on safety and high-efficiency mining, the mechanical parameters of coal and roof and floor were tested in the laboratory. Comining with slip-line theory of floor damage rock mass, floor damage partitions were given after the upper coal seam mining. It calculated the floor damage degree of the upper coal seam mining with the distinct element numerical software. And distribution curves of maximum concentrated stress along the horizontal direction and vertical direction of floor were conclude d. The results showed that after the upper coal seam of contiguous coal seams mining, the thickness of floor damaged rock strata increased linearly along the floor verti cal direction. Along the floor horizontal direction, the rock plastic damaged zone extended by fan shape, and its maximum thickness was at the edge of working face.