Abstract: Taking Xi’an Mine as an example, it is found that the sudden drop of the atmospheric pressure causes the abnormal increase of gas emission in underground return airflow, and the abnormal gas emission usually lags behind the pressure drop of about 3-6 h. The abnormal gas emission curve is divided into three types: “polar peak”, “fluctuation” and “fluctuation + polar peak”. The basic principle of the atmospheric pressure affecting the gas concentration of return air flow in the underground mining face is analyzed. It is considered that the absolute value of the air pressure of the roadway affects the “desorption and adsorption” speed of the coal pore wall gas. The pressure gradient caused by the relative change of the air pressure of the roadway affects the gas migration velocity in the pore and fracture. Combined with the measured data, the quantitative equation of the change of the return gas concentration with the atmospheric pressure in the residual coal recovery face under the initial surface pressure is obtained. Finally, according to the influence of the atmospheric pressure drop on the gas emission, two kinds of prevention and control ideas are proposed to cut off the gas migration channel or to offset the atmospheric pressure drop.