Selected ionic liquids are known to enhance the absorption of CO2 for CO2 removal purpose. In the idea to improve the membrane separation performance for natural gas sweetening, ionic liquid modified polymeric membranes were fabricated by using polyethersulfone (PES) and blended with different composition of ionic liquid which are 5 wt and 15 wt. Each fabricated membranes were prepared and dried under solvent evaporation at 90°C. Dense structure observed from FESEM analysis indicated the miscible blends of ionic liquid and PES. TGA analysis showed all fabricated membranes are still containing solvent and this resembles that membrane drying period is still insufficient. All fabricated membranes were tested with ideal gas permeation test. From the result, the addition of ionic liquid has enhanced the ideal CO2 pemeance about 150 as compared to pure PES membrane. The ideal CO2/CH4 selectivity was also increase about 85 from the base but however, the separation index is still considered low and this may due to the presence of the solvent. This preliminary result has confirmed that the blending of ionic liquid with pure PES membrane has technically improved the membrane separation performance. Copyright © 2014 Trans Tech Publications Ltd, Switzerland.