The selective reduction of sulfur dioxide with carbon monoxide to elemental sulfur was studied over AC-supported transition-metal oxide catalysts. According to the study, Fe2O3/AC was the most active catalyst among the 4 AC-supported catalysts tested. By using Fe2O3/AC, the best catalyst, when the feed conditions were properly optimized (CO/SO2 molar ratio = 2: 1; sulfidation temperature, 400 degrees C; Fe content, 20 wt%; GHSV = 7000 mL g(-1) h(-1)), 95.43% sulfur dioxide conversion and 86.59% sulfur yield were obtained at the temperature of 350 degrees C. Catalyst samples were characterized by X-ray powder diffraction in order to relate the phase composition to the activation behavior and catalytic performance. The active phase of catalyst was detected as FeS2, and the formation of FeS2 was greatly dependent on the sulfidation temperature.