Abstract: In this paper, mercury intrusion experiment and high pressure isotherm adsorption experiment were used to analyze the pore structure characteristics and gas adsorption capacity of different metamorphic degrees of coal. Combined with industrial analysis data of coal samples, further investigate the effect of pore structure characteristics on coal seam gas permeability is carried out. The research shows that: the mercury porosities of the two kinds of coal samples show a trend of changing from high to low with the increase of coal ranks; the pore size distribution of Songhe No. 3 coal sample shows the single peak characteristic of the tiny pore size; the pore size distribution of Linhua No.9 coal sample shows the double peak scharacteristics of small pore diameter and medium and large pore diameters; the gas adsorption capacity of Songhe No. 3 coal measured by high pressure isotherm adsorption experiment is stronger than that of Linhua No.9 coal. The conclusion is that the pore characteristics, porosity and gas adsorption capacity of coal are affected by the degree of coal metamorphism, and the features of low metamorphic coal are outstanding.