The flow of gas in the coal bed is an extremely complex process, and the quantity of gas emission is mainly affected by both gas pressure in coal seam and permeability coefficient of coal seam. The influence factors of quantity discharge of firedamp from coal drift of headwork surface are analyzed, and the characteristics of discharge of firedamp from coal drift of headwork surface are closely related to the factors such as geological structure, gas content, gas pressure and permeability of coal seam. Not only the mathematical and physical model of one-way fluxion of discharge of firedamp from coal drift of headwork surface is established, but also the calculation formula of the quantity discharge of firedamp from coal drift is obtained by applying of variable separation method. According to the formula, the stagnation movement, which is among coal unloading pressure zone of stress, the stress concentration zone and original stress zone stress stagnation and the firedamp package of phenomenon, is analyzed in the coal and gas outburst mine. While the gas permeability of coal seam correspondingly changes variation, the quantity gas discharge also has the corresponding dynamic change. The results show that when the coal body in front of coal drift is in a non equilibrium state in the interaction among the horizontal crustal stress by gravity, gas pressure and mechanical properties of the coal, there is a risk of coal and gas outburst. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.