Abstract: Through low temperature nitrogen absorption test of different coal structure, we found that pore volume of each aperture segment does not correspond with the specific surface area ratio, in particular, pore volume of micro-pore is small, but it has larger specific surface area. Compared with the native structure of coal, symbiotic structure coal increased the specific surface area and pore volume at various stages. Coal reservoir porosity is the main gathering place for gas, but also its migration path; pore structure not only restricts the gas content of coal, but also has an important impact on the desorption and diffusion.