Selective adsorption of CO2 from its mixture with CH4 on several commercial molecular sieves was studied at ambient temperature(25℃) and low pressure (0.2MPa). The behaviours of the molecular sieves were compared by using three basic parameters: selectivity, adsorption capacity and regenerability. The results indicate 3A and 4A molecular sieves have low CO2 adsorption capacity. However 5A and 13X molecular sieves show high efficiency in dynamic separation of CH4 and CO2 when the adsorbents are used for the first time. The separation coefficient between CH4 and CO2 on 13X molecular sieve is higher than 5A, which proves 13X molecular sieve show better performance in separating CO2 from its mixture with CH4. But 5A and 13X molecular sieve could not be regenerated completely by vacuuming and the adsorption/regeneration performance became stable from their second use. The reason why separation performance of 5A and 13X molecular sieves decrease is explained by FTIR spectroscopy that the partial poisoning of the molecular sieves happened. That is to say the regenerability of the two molecular sieves need improve.