Abstract: To study the effect of carbon dioxide on coal spontaneous combustion characteristics, the thermogravimetry-mass spectrometry technology was used to test the oxidative combustion process of Yangquan No.5 coal mine under different φ(CO2)/φ (O2) ratios. We analyzed thermogravimetric curves, characteristic temperature point, heat release and gas escape laws. The results show that as the ratio of φ(CO2)/φ(O2) increases, the thermogravimetric curve shifts to high temperature, the characteristic temperature point increases, the intensity of combustion decreases, and the gas escape temperature increases. Before the temperature is less than 360 ℃, the difference in exothermic heat is small. As the temperature continues to rise, at the same temperature, the heat release decreases as the oxygen concentration decreases. Since carbon dioxide reacts with hydrogen to produce CH4, the higher the carbon dioxide content, the higher the CH4 intensity. At the same time, coal is more prone to incomplete combustion at low oxygen concentrations, so more CO is produced. Compared with air atmosphere, the concentration of carbon dioxide is higher than 88%, which has an inhibitory effect.