Abstract: The free CO₂ storage capacity increases gradually with the buried depth in the deep coal seam. The free CO₂ storage capacity was calculated and its change with depth was preliminarily analyzed, based on the tested data of coal samples in the south of Qinshui basin, Shanxi Province. The results show that the storage capacity is affected by porosity, gas saturation, temperature, pressure, etc. The capacity increases with the change of physical properties of CO₂ injected into the coal, but varies with the size of the experimental particle of the coal. The porosity of coal reservoir decreases significantly with depth of coal under effective stress, and the storage capacity of CO₂ is significantly reduced, and also, the capacity increases with the gas saturation.