Three kinds of ionic liquids (ILs) with ether-functionalized cations and bis(trifluoromethanesulfonyl)imide anions were synthesized in our laboratory, and the SO2 absorption capacities of those three kinds of ILs were measured at temperature from 20 to 50 degrees C and 1 bar. High capacity of SO2, excellent reversibility, and high selectivity were achieved by the interaction between the ILs and SO2. The absorption and desorption processes are very fast, and SO2 can be removed completely from the ILs. Thermal stability was tested, and the decomposition temperatures of the three kinds of ILs were all higher than 420 degrees C. NMR investigations and computer simulation studies also show that SO2 absorption by these ILs is a physical process by forming weak hydrogen bonds between the oxygen atoms in the SO2 and the hydrogen atoms in the ILs. This work further investigated how the water content affects the solubility of SO2 in the ILs. These ILs exhibit significant improvements over traditional absorbents and indicate green, efficient, and energy-saving methods for industry applications in SO2 separation.