Abstract: In view of problem of spontaneous combustion of VI-15, VI-16, VI-17 and VI-18 coal seams in Pingdingshan No.10 Coal Mine, temperature programmed oxidation experiment was used to analyze change of gas production quantity in each coal seam, and coal seam index gas were determined. Propane can be used as index gas of VI-15 coal seam, ethane can be used as index gas of VI-16 coal seam, and CO can be used as index gas of VI-17 and VI-18 coal seam. The experimental data were imported into Matlab software for curve fitting, so as to obtain fitting relationship equation between production quantity of index gas and temperature of coal seam. Temperature and production quantity of index gas of coal seam in different periods were measured through drilling holes arranged on site. The temperature measurement data were substituted into the fitting relationship equation, so as to obtain calculated data of production quantity of index gas. The calculated data is basically consistent with the actual measurement data, which verifies the validity of the fitting relationship equation.