Abstract: Taking the meager coal, lean coal and anthracite before and after the influence of magmatic intrusion in 2₁ coal seam of No.13 coal mine of Pingdingshan Coal Mining Group as research objects, the mercury intrusion porosimetry(MIP) was used to study the influence of thermometamorphism on the development characteristics of pores of coal. The experimental principles of MIP, the calculation process of the total specific surface area and the total pore volume were summarized in detail. The distribution of pore volume and specific surface area in different aperture and the fractal dimension of pore between 5.5 nm and 350 μm were also discussed. The results show that many new pores were created due to magmatic intrusion, so the pore volume and the specific surface area increased significantly, while the median pore diameter and volume as well as the average pore diameter decreased, indicating that the new pores are mainly concentrated in the small aperture. The change rules of the fractal dimension indicate that the magmatic intrusion caused the enlargement of the roughness, the absorbability and distribution range of the intraparticle pore.