Abstract: In order to study the pore characteristics and gas desorption law of No.8 seam structure coal and the primary structure coal in Wolonghu Mine, the merc ury intrusion porosimetry and the adsorption experiment were individually applied to the experiment study on four groups of the coal samples. The experiment results sh owed that the percentage of the medium and large pore's pore volume in the structure coal would be higher than the primary structure coal, the structure role would hav e obvious reconstruction effect to the medium and large pores of the coal and new micro pores and small pores would be occurred. The specific surface area sum of the micro pores and small pores in the structure coal would individually take 98.85% and 98.74% of the total specific surface area, and the specific surface area sum of the micro pores and small pores in the primary structure coal would individually take 99 .52% and 99.37% of the total specific surface area.Therefore, the micro pore and sm all pore would determine the specific surface area and would be the main adsorption space of the gas in the seam. Meanwhile, the gas desorption capacity of the struct ure coal was obviously higher than the primary structure coal in a same coal rank and due to the structural coal with many medium and large pores in the structure coal, those pores could provide the channels of the gas migration. The reconstruction of the coal pore structure by the structure role would be affected to desorption perform ances of the coal would increase the danger of the coal and gas outburst.