Three guanidinium-based ionic liquids (GBILs) including [1,1,3,3-tetramethylguanidinium][phenol] ([TMG][PHE]), [1,1,3,3-tetramethylguanidinium][2,2,2-trifluoroethanol] ([TMG][TE]) and [1,1,3,3-tetramethylguanidinium][imidazole] ([TMG][IM]) were synthesized and their absorption and desorption of sulfur dioxide were investigated, respectively. The saturated molar ratio of SO(2) to GBILs varied from 2.24 to 3.16 at 40 degrees C with high absorption rate. The absorption mechanism might be that SO2 reacts with the -NH(2) group on the cation and then a new -SO(2)H group is formed. The new GBILs could absorb SO(2) by both physical and chemical interactions while physical absorption does play an important role at the experimental conditions under investigation. (C) 2011 Elsevier B.V. All rights reserved.