Abstract: In this study, low rank bituminous coal was 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 and dense to loose and porous before and after preparation, 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 showed that prepared CACs have a high selectivity for methane and nitrogen mixture at low pressure. But when pressure is higher, the selectivity increases more rapidly with increasing molar fraction of methane in the gas phase. Also, selectivity is mainly affected by micro-pores in the range of 0.55 to 0.85 nm, while meso-pores and macro-pores are not selective.