The group contribution lattice fluid equation of state (GCLF EOS) was first extended to predict the thermodynamic properties for carbon dioxide (CO 2 )-ionic liquid (IL) systems. The group interaction parameters of CO 2 with IL groups were obtained by means of correlating the exhaustively collected experimental solubility data at high temperatures (above 278.15 K). New group parameters between CO 2 and IL groups were added into the current parameter matrix. It was verified that GCLF EOS with two kinds of mixing rules could be used for predicting the CO 2 solubility in ILs, and volume expansivity of ILs upon the addition of CO 2 , as well as identifying the new structure-property relation. Moreover, it is the first work on the measurement of the solubility of CO 2 in ILs at low temperatures (below 278.15 K), manifesting the applicability of predictive GCLF EOS over a wider temperature range.