Abstract: A micropore activated carbon (AC-1) with 1943m2/g specific surface area and an activated carbon (AC-2) with 1567m2/g specific surface area and 47.18% mesopores were prepared. Adsorption isotherms of CO2，CH4，N2 and O2 on AC-1 and AC-2 were determined at 298K and the adsorption separation properties of the activated carbons for the mixtures of CO2/N2，CO2/CH4 and CH4/N2 were discussed. The results showed that the pore structure was the main factor affecting the adsorption separation properties of the activated carbons. AC-2 which with many mesopores was more suitable for the adsorptive separation of the mixtures of CO2/N2，CO2/CH4 than AC-1 with only micropores，while AC-1 was more suitable for the adsorptive separation of CH4/N2 than AC-2.