Impact of Si/Al ratio on the adsorption capacity and separation selectivity of CO2/CH4 in SAPO-34 has been investigated. SAPO-34 samples were synthesized with two Si/Al ratios (0.2 and 0.3). A batch adsorption volumetric apparatus was used to measure the adsorption equilibrium capacity and derive the equilibrium isotherms. The tests were performed in a wide range of pressure from normal to 3000kPa and three levels of temperatures from 277 to 298K. Results proved decreasing Si/Al ratio, from 0.3 to 0.2, improved CO2 separation from CH4.