Abstract: The adsorption separation of CO2，CH4 and N2 was studied via volumetric measurements of β-zeolite samples with different SiO2/Al2O3 ratios at 273 and 303 K. Results showed that all the obtained adsorption isotherms are well correlated with the Langmuir-Freundlich model. For a certain sample，the adsorption capacity for CO2 is much higher than that for CH4 and N2. The adsorption capacity for CO2 increases with the decrease in SiO2/Al2O3 ratio under same temperature and pressure. The Henry law′s constant and adsorption equilibrium selectivity of CO2，CH4，and N2 on different β-zeolite samples were calculated via Virial equation，showing that the β-zeolite samples have higher equilibrium selectivity for CO2 over N2 and CH4. The selectivity of CO2 over N2 and CH4 increases with the decrease in SiO2/Al2O3 ratio. Therefore，the β-zeolite sample with a low SiO2/Al2O3 ratio is a good candidate for the separation of carbon dioxide from its mixture with methane and nitrogen. The isosteric adsorption heat for CO2，CH4 and N2 calculated by Clausius-Clapeyron equation is independent with the increase of adsorption loading，which indicates thatβ-zeolite is an energetically homogenous adsorbent.