Abstract: In order to study the diffusion characteristics of CO₂ in low-permeability raw coal under subcritical conditions (gas pressure lower than 6 MPa and temperature lower than 39 ℃), the CO₂ adsorption/desorption experiments and diffusion experiments were carried out by the volumetric method to study adsorption/desorption and diffusion characteristics of CO₂ in raw coal. The results show that the increase of pressure will promote the adsorption of CO₂ by coal, and the increase of temperature will inhibit the adsorption of CO₂ by coal, and there is a desorption hysteresis phenomenon in the adsorption/desorption process of CO₂ in raw coal. When the equilibrium pressure is constant, the diffusion amount of CO₂ in the raw coal at different temperatures is positively related to the diffusion time, the CO₂ diffusion rate is inversely proportional to the diffusion time, and the CO₂ diffusion coefficient D increases with the increase of temperature. Under the medium and low pressure environment, the temperature change within a certain range (15-35 ℃) has little effect on the diffusion rate of CO₂ in the raw coal. When the equilibrium temperature is constant, the amount of CO₂ diffusion in the raw coal under different pressures is proportional to the diffusion time, the CO₂ diffusion rate is inversely proportional to the diffusion time, and the CO₂ diffusion coefficient D increases with the increase of pressure; when the temperature is 15 ℃, within a certain range, the pressure change (0.5-3.5 MPa) has very little effect on the diffusion rate of CO₂ in the raw coal.