Abstract: In order to solve the problem of early accurate prediction of spontaneous combustion in gassy coal seam of Jianbei Coal Mine, taking the coal seam of 4204 working face of the mine as the research object, the programmed temperature test was mainly used to analyze the variation law of CO, CO₂, C₂H₆, C₂H₄ gas volume fraction in the process of temperature rising oxidation of coal samples with different particle sizes, and the treatment and analysis were carried out by means of Grignard fire coefficient. The results show that the critical temperature of CO in Jianbei Coal Mine is 60 ℃ to 80 ℃, and the overall change trend is growing exponentially, and the relationship between CO gas production and particle size is inversely proportional; the temperature at which C₂H₄ appears is about 120 ℃, and the smaller the coal particle size is, the faster the volume fraction increases.According to the principle of index gas optimization, the optimal indexes of spontaneous combustion of gassy coal seam in 4204 working face of Jianbei Coal Mine are determined as follows: CO and the second type fire coefficient are the main gas indexes; C₂H₄, alkene ratio φ(C₂H₄)/ φ(CH₄) and φ(C₂H₄) / φ(C₂H₆), and the third type of fire coefficient are auxiliary gas indexes. The gas index CO and coal temperature are used for function fitting to further verify the degree of coal spontaneous combustion. The research results provides a theoretical basis for the prediction of spontaneous combustion of gassy coal seam in Jianbei Coal Mine, and has important guiding significance for the early prediction and advanced prevention and control of spontaneous combustion of gassy coal seam under similar working conditions in China.