Abstract: CO is an important indicator gas in the early warning system of coal spontaneous combustion. To improve the accuracy of using CO to predict the risk degree of coal spontaneous combustion in goaf under air leakage conditions, programmed temperature rise experiments is used to analyze the corresponding relationship between different indicator gases and coal temperature during coal oxidation process. Through bundle tube monitoring and tracer gas leakage testing, the impact of leakage on CO gas in goaf is determined, and the functional relationship between CO volume fraction and coal temperature in different oxygen volume fraction ranges is corrected. Using the modified function equation to calculate the CO early warning threshold of coal spontaneous combustion, combined with the early warning value of different index gases, the classification early warning system of coal spontaneous combustion in goaf under the condition of air leakage is constructed. The research results indicate that there is a characterization relationship between the sudden changes in index gas of CO, C₂H₄, C₂H₂ and Graham coefficient during coal oxidation process and coal temperature. The initial temperatures of CO, C₂H₄, and C₂H₂are 30 ℃, 120 ℃, and 230 ℃, respectively. The turning point temperatures of the Graham coefficient are 70 ℃ and 160 ℃, respectively. The relationship between CO volume fraction and coal temperature in different oxygen volume fraction ranges is exponential function. The influence range of air leakage on CO gas in goaf is 0−90 m, and the influence volume fraction is (3−39)×10⁻⁶. Under the condition of air leakage, the oxygen volume fraction range at a depth of 0−19 m in the goaf is 21%−17%, and the correction coefficient of the CO volume fraction coal temperature function is 1−3. The oxygen volume fraction range at a burial depth of 19−55 m is 17%−13%, with a correction factor of 4−7. The oxygen volume fraction range at a burial depth of 55−90 m is 13%−9%, with a correction factor of 16−21. Based on the modified CO volume fraction and temperature function, the CO warning thresholds for coal spontaneous combustion process in different oxygen volume fraction ranges are calculated to be (50−150)×10⁻⁶, (190−330)×10⁻⁶, and (330−430)×10⁻⁶, respectively. Combined with the early warning value of CO, C₂H₄, C₂H₂ and Graham coefficient index, the coal spontaneous combustion is divided into five warning levels of gray, blue, yellow, orange and red. The research results can provide reference for the prediction and prediction of spontaneous combustion of residual coal in goaf of similar working face.