Abstract: In order to investigate the influence of different humidity conditions on the parameters and thermal effect of the process of coal spontaneous combustion, a compact air generator with adjustable humidity was built and used in conjunction with the temperature program oxidation device of coal spontaneous combustion to measure the release law of indicator gas during coal spontaneous combustion process. Thermal analysis equipment was used to quantitatively characterize the law of heat release from spontaneous combustion of coal under different air humidity conditions. The influence of air humidity on the thermal effect of coal spontaneous combustion was studied by numerical simulation method. The results show that the ventilation of moist air can significantly increase the oxygen consumption rate of coal samples and promote the production of CO and CO₂. The thermal effect of air humidity on the spontaneous combustion of coal presents stage characteristics. When the moisture in the air first contacts with the coal, it will release a large amount of adsorption heat in a short time, promoting the rise of coal temperature. The moisture in air participates in the thermal effect of coal spontaneous combustion system mainly through four ways: adsorption heat of water, reaction heat of coal oxygen, heat convection and heat conduction, among which the adsorption heat and the conduction heat play leading roles.