The catalytic reduction of SO2 to sulfur element by reacting with CO over supported iron and iron-lanthanum catalysts was investigated. This investigation had the following experimental condition: temperature range of 350 ~ 550 ℃, initial SO2 concentration of 1000 ~ 10000 ppm, CO/SO2 molar ratio of 1.0 ~ 3.0 and space velocity of 5000 ~ 12000 h(-1). The SO2 conversion and selectivity to sulfur element were measured in a differential fixed bed reactor at atmospheric pressure. The catalyst prepared by wet impregnation of 10 wt% iron on γ-Al2O3 showed that at temperature above 400 ℃, SO2 conversion was higher than 95% and COS yield was less than 4%. The optimum CO/SO2 molar ratio was estimated as 2.0 At a higher CO/SO2 molar ratio, the SO2 conversion increased but the COS yield became higher than 20%. The effect of SO2 concentration and space velocity for SO2 conversion and COS yield was insignificant in the experimental range. The active phase of the activated iron catalyst was identified as FeS2 by X-ray diffraction. The FeS2 phase remained unchanged after the reaction.