Abstract: Accurately determining the limit value of gas content for prediction of area prone to gas outburst has the instructive function to improve targeted outburst prevention and reduce cost. The paper, taking seamⅡ₁ of Longshan mine as an example, on the basis of measuring lots of gas parameters, analyzed the outburst characteristics in Longshan mine and studied adsorption characteristic of seamⅡ₁. A lot of gas content and prediction indexes were measured and their relation was studied. The results show that the metamorphism degree of seamⅡ₁ is high with strong adsorption ability, and it can adsorb more methane under the same gas pressure, eventually it was determined that the limit value of gas content is 10.0 m³/t.