Abstract: Changing rule of composite gas indexes under different dry air flow and oxygen concentration was analyzed through coal temperature-programmed experiment. The experimental results show that φ(O2)/(φ(CO)+φ(CO2)) should be selected as gas indexes for coal spontaneous combustion prediction in the case of uncertain dry air flow. φ(O2)/(φ(CO)+φ(CO2)) can be used as gas indexes for coal spontaneous combustion prediction when coal temperature is below 100 °C. φ(C2H4)/φ(CH4) and φ(CO)/φ(CO2) can be used as gas indexes for coal spontaneous combustion prediction when coal temperature exceeds 100 °C. φ(C2H4)/φ(CO) can also be used as gas indexes for coal spontaneous combustion when coal temperature exceeds 160 °C and oxygen volume fraction is approximately 5%.