By using the theory of geology and gas geology and combining exploration and mine production, sampling experiments, field measurement and a large underground coal wall observations and other information, the main factors affecting the 3^# coal seam gas in Xinjing coal mine was studied. The results showed that the degree of metamorphism and coal－bearing sedimentary rock environment of 3^# coal seam gas provides a good "life" as "reservoir" condition for gas; and mine field sturcture, coal cap, the hydrogeological characteristics of 3^# coal seam gas provides a favorable preservation conditions, coupling relationship between the main factors that have joint control of its occurrence rule. The results help to improve the relevance and effectiveness of mine gas prevention and control.