Abstract: In order to study coal seam fire evolution and the influence of the decrease of air amount on coal spontaneous combustion gaseous products, the experimental device for testing coal spontaneous combustion characteristic parameters is carried out to do temperature-programmed experiment under the condition of reducing air volume, and coal spontaneous combustion process and laws on taking measures about plugging the air leakage channel and reducing air leakage at coal mine site after critical temperature are simulated. The results show that the amount of air leakage has little influence on the range of dryness temperature; the volume fraction of each gas product has similar characteristics with the variation of wind volume, that is, the decrease of air volume accelerates the production of gaseous products at the range of 80 ℃ to 140 ℃, and restrains acceleration after 140 ℃.