Mine geological structure features, roof and floor lithologic and depth of coal seam were analyzed, depth of coal seam was the largest influencing factor of coal seam gas content, measured parameters of gas underground and geological exploration of gas parameters were compared and corrected, gas occurrence law of No. 4 coal seam was found out, which provided theory foundation for gas control. The maximum gas content was got based on gas occurrence law of the coal seam, and the maximum gas emission content was deduced, the composition of the gas emission was analyzed, which provided reference for the corresponding measures of gas control.