Abstract: In order to study the pore structure characteristics of low permeability coal, we carry out experiments on M9 anthracite soft seam of Guiqing Coal Mine by low temperature nitrogen adsorption method and mercury intrusion method. The results show that the pore size distribution of coal is extensive and develops from micropores to visible holes and cracks. The micropore which is in favor of gas storage with the most distributed development and has the largest surface area, which accounts for more than 98% of total surface area. However, large pores, medium pores and fractures, which form infiltrated volume, are less development. The adsorption-desorption curve and the advance and retreat mercury curve of coal are both not overlap. Both the desorption curve and the retreat mercury curve have inflection point. And the efficiency of retreat mercury is low. All of these show that impermeable pores and neck bottle type holes closed at one end in coal, which could lead to poor permeability, be not conducive to the gas diffusion and seepage, and reduce the extraction efficiency, be prone to coal and gas outburst.