Subscript textCO2 emission control is an important issue, in which chemical absorption process has reached the widest application. Ionic liquid is a kind of green solvent and expected to take the place of traditional amine absorbents as for its better characteristics. In this paper, two iminazole base ionic liquids were synthesized, including of bromide 1-butyl-3-methylimidazo ([bmim]Br) and 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6). The performance of CO2 absorption by [bmim]PF6 and [bmim]Br were compared under the same other conditions. Subscript textIt indicates that [bmim]PF6 has more absorption capacity and less saturated absorption time under low temperature, which provides reference for CO2 control by ionic liquid.