Abstract: Taking the underside protective layer mining in the working face of Panyi Coal Mine as the research object, based on the theory of coal rock deformation and gas flow under the condition of protective layer mining, it is concluded that the actual pressure-relief angle is greater than the theoretical pressure-relief angle by the numerical simulation analysis for stress and deformation characteristics, coal seam permeability rule of protective layer overlying strata. There is a transitional distressed zone between original coal and full pressure-relief zone, so is the coal seam permeability coefficient. Gas extraction measures can effectively eliminate the outburst danger in the transitional distressed zone, and expand the protection scope further.