Abstract: Carbon monoxide (CO), as a crucial indicator gas for predicting the early spontaneous combustion of coal, is mainly derived from the spontaneous combustion of residual coal in gobs. In North China, bituminous coal reserves are abundant, and due to their low metamorphism degree, such coal is more prone to spontaneous combustion and tends to oxidize to produce CO gas at low temperatures. For instance, in the gobs of some coal mines, even though there are no signs of coal spontaneous combustion, the CO concentration at the working face continuously exceeds the limit, which leads to misjudgments in the prediction and early warning of early coal spontaneous combustion. To address this problem, a combined method of experimental research and theoretical analysis was adopted. Crushing experiments were carried out on two types of bituminous coal with different metamorphism degrees (gas coal and coking coal) under nitrogen and air atmospheres to simulate the crushing process during working face mining, and analyze CO volume fraction and coal sample temperature changes. Furthermore, low-temperature water bath-gas chromatography experiments, low-temperature nitrogen adsorption experiments, and Fourier transform infrared spectroscopy (FTIR) experiments were conducted to analyze the abnormal sources and generation characteristics of CO from both macroscopic and microscopic perspectives. The results show that: in an air atmosphere, the volume fractions of CO generated by the crushing of gas coal and coking coal both exhibited an exponential growth trend, reaching maximum values of 55.62×10⁻⁶ and 17.83×10⁻⁶, respectively, whereas in a nitrogen atmosphere, the volume fractions of CO generated by the crushing of both coals did not exceed 2×10⁻⁶; during the low-temperature water bath oxidation process, the maximum volume fractions of CO produced by gas coal and coking coal reached 2 295×10⁻⁶ and 527×10⁻⁶, respectively; the results of low-temperature nitrogen adsorption experiments indicated that during the low-temperature water bath process, the average pore diameter of gas coal increased from 11.381 nm to 17.586 nm, and the specific surface area increased by 35.8% (from 2.179 m²/g to 2.961 m²/g), the proportion of macropores in gas coal increased from 18% to 23%, and the proportion of micropores decreased from 12% to 3%; the average pore diameter of coking coal increased from 11.615 nm to 14.694 nm, and the specific surface area increased by 37.9% (from 2.803 m²/g to 2.867 m²/g), the proportion of macropores in coking coal increased from 12% to 20%, and the proportion of micropores decreased from 23% to 7%; Fourier transform infrared spectroscopy experiments further analyzed the oxidation reaction process of functional groups such as aliphatic hydrocarbons under low-temperature conditions, revealing that CO is mainly derived from the thermal decomposition of carbonyl groups.