Abstract: For figuring out the mechanism of the influence of atmospheric pressure on gas emission, the static pressure's relations on surface, in coal face and goaf are experimentally studied, the change of gas concentration in goaf during atmospheric pressure fluctuation is explored, and the prevention and control system of Laohutai coal mine is introduced.The static pressure in coal face changes synchronously with the atmospheric pressure, but the change in the goaf has obvious hysteresis.The air pressure difference in the goaf caused by the hysteresis is the direct cause of gas emission.Regarding the gas concentration in goaf, when the statistic pressure decreases in the coal face, the gas concentration in goaf increases, presenting a significantly negative correlation.The prevention and control system of Laohutai coal mine consists of monitoring the atmospheric pressure, enhancing the gas drainage in goaf, and increasing the air volume.This system can effectively control the abnormal gas emission caused by the rapid and continuous reduction of atmospheric pressure.