In this study, low rank bituminous coals were used as raw material for the preparation of a series of coal-based activated carbons (CACs) with similar surface properties but different pore structures, and these CACs could be used to enrich methane from low concentration gas by pressure swing adsorption (PSA) method. The surface morphology of raw material changed from smooth to porous after activating reaction. In addition, the high-pressure adsorption isotherms of methane and nitrogen indicated that the adsorption performance of CACs for methane is stronger than nitrogen. The prediction results by Ideal Adsorbed Solution Theory (IAST) method also shows that prepared CACs have a high selectivity for methane and nitrogen mixture at low pressure. At higher-pressure conditions, the selectivity increases more rapidly with increasing molar fraction of methane in the gas phase. In addition, selectivity is mainly affected by micropores in the range of 0.55-0.85 nm, while mesopores and macropores have no effects on the selectivity. Present research results would provide some guidance for the preparation of excellent adsorbents and improve the efficiency of adsorption separation. (C) 2017 Elsevier B.V. All rights reserved.