Nitrogen adsorption method is divided into dynamic chromatography and static method according to the different methods of adsorption and adsorption. Dynamic chromatography is to install the powder sample to be tested in a U-shaped sample tube, and to make a mixed gas containing a certain proportion of adsorbate flow through the sample, and determine the accuracy of the sample to be adsorbed by the gas concentration change before and after adsorption. Defects such as high equipment requirements are rarely used. Another possible method is to use CO2 as the adsorbate for adsorption at room temperature, which eliminates the need for a vacuum in the molecular turbo pump stage. The specific surface area, micropore diameter and micropore volume can be conveniently obtained, and are applied in the analysis of microporous materials such as activated carbon, and the effect is very good. Adsorption isotherms are sources of information about the pore structure of the adsorbent, heat of adsorption, and other physicochemical characteristics. Under a constant temperature and a wide range of relative pressure conditions, the adsorption isotherm of the adsorbate is larger than the surface, the surface of the particle is less smooth, and the surface area is larger, and the surface of the particle has a larger hole than the surface. It is amazing that only one gram of powder expands their specific surface area to reach tens, hundreds or even thousands of square meters. The adsorption amount of the adsorbed molecules (N2) of the sample to be tested is determined according to the pressure or weight change before and after the adsorption; the volumetric method is to load the sample to be tested into a closed tube-shaped sample tube of a certain volume, and inject into the sample tube. A certain pressure of adsorbate gas.