In order to further grasp the gas concentration distribution law of the U-ventilation comprehensive mining working surface, 12508 working face of Tunlan Mine was taken as the study background, and the on-site monitoring test plan of the gas concentration of the work surface was proposed, the test results showed that the gas concentration gradually increased along the work surface from the inlet side to the return side, and reached the highest concentration of 0.63% in the corner of the return wind; the tendency of the work surface from the coal wall side to the side of the mining area, the gas concentration showed the "high-low-high" change law. Therefore, in order to prevent and control the return wind on the corner of the gas over the limit, should be optimized from the ventilation program, hanging wind tent, buried pipe in the mining area, reduce the pressure difference and other aspects of the gas management.