Through a multi-phase separation process with the use of room temperature ionic liquid (RTILs) and polymer, new supported ionic liquid membranes (SILMs) were developed for the removal of acidic gases from crude natural gas. PVDF (poly vinylidene fluorolide) and BMImBF(4) were used as polymer materials for membrane and RTILs respectively. The structure of SILMs was characterized with SEM. To investigate the permeation properties, the SILMs were tested with CO2, H2S and CH4 at various operating conditions. Since CO, and H2S have higher affinity toward RTILs than CH4, the permeability coefficients of these two acidic gases were found to be considerably high at 30-180 and 160-1100 barrer, respectively. Moreover, the selectivity of CO2/CH4 and H2S/CH4 were found to be 25-45 and 130-260, respectively.