Abstract: In order to study the effect of liquid-solid expansion phase change on coal permeability enhancement under thermal environment, based on the experiment of increasing the permeability of coal by thermal storage phase change, the characteristics of coal permeability and T₂ relaxation time spectrum changes under the effect of thermal storage phase change are obtained, and the effects of thermal storage phase change on coal permeability and pore structure were analyzed. The research results show that the maximum increase in coal permeability under the effect of thermal storage phase change reaches 150.8%, the thermal environment provided by the thermal storage phase change can promote the effect of phase change expansion on the increase of the coal permeability. The peak of the coal body T₂ relaxation time between 10 ms and 50 ms and about 100 ms rises relatively higher, the increase is 15.36% and 18.03%, and the maximum increase of the T₂ value between the two peaks is 47.11%. The thermal storage phase change mainly increases the permeability of coal by increasing the number of medium and large pores and cracks, and the structure connectivity between the two.