To explore environmentally benign solvents for absorbing SO2, a series of caprolactam tetrabutyl ammonium bromide ionic liquids were synthesized, the solubilities of SO2 in which were measured at (298.2 to 403.2) K and atmospheric pressure. The solubilities of SO2 in these ionic liquids were 0.680 at 298.2 K and ambient pressure and decreased sharply as temperature increased and increased with the increasing mole ratio of caprolactam. A fifth-order polynomial was proposed and verified by experimental Solubility data. The absorption and desorption of SO2 were practically reversible in the synthesized ionic liquids.