CO_2 solubility in diethyl carbonate(DEC), ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide([Bmim][NTf_2]), and their mixtures at various mass ratio were measured isovolumetrically at temperature of 308.15—328.15 K and pressure of 0—3 MPa. Effect of [Bmim][NTf_2] on DEC vapor pressure was studied using COSMO-RS model. The experimental results showed that CO_2 solubility in DEC and [Bmim][NTf_2] increased with increasing pressure at constant temperature but decreased with increasin...