Five types of active carbon’s adsorption isotherm of nitrogen at 77K were measured, and their adsorption characteristic were analysed. The results show AC1, AC2 and AC3 have a lot of micropores for they have high nitrogen adsorbance in low pressure at 77K. The HK model was employed to analysis the pore size distribution of the adsorbance. AC1 has most developed microspore structure, its surface area reached 1706㎡/g, and its pore size mainly concentrated at 4.6 angstroms. Then the five adsorbents’ adsorption isotherm on methane, oxygen and nitrogen at 298K, 308K and 318K were measured. Methane’s adsorption capacity on active carbon is much higher than nitrogen and oxygen, and the adsorbance of nitrogen and oxygen have little difference, so the coal mine methane could be regarded as the binary of methane and nitrogen on methane separation by adsorption method. AC1 has the highest methane adsorbance and equilibrium selectivity factor of methane to nitrogen. Then the adsorption heat was studied, the results show that the isosteric heat of methane on AC1 decreased from 20.6kJ/mol to 19.55kJ/mol when the adsorbance of methane increases from 0.4 mol/kg to 1.2mol/kg, and methane’s adsorption heat is higher than nitrogen.