Hydrogenation of sulfur dioxide to hydrogen sulfide was investigated over a series of gamma-Al2O3 supported iron catalysts with Fe/gamma-Al2O3 weight ratios of 0.01-5. These catalysts were prepared by a slurry method using iron sulfate and iron nitrate as the iron precursors. Surface areas of these catalysts decreased continuously with the increase of iron loading. The hydrogenation was carried out in a flow reactor at a temperature range of 180-400 degreesC, elemental sulfur was found to be the sole sulfur product when SO2 conversion was <70%. Catalyst activity, evaluated in terms Of SO2 conversion and the incipient reaction temperature needed to achieve 100% H2S yield, depended strongly on its composition. The optimum Fe/gamma-Al2O3 weight ratio was found to be 2-3 in spite of the difference in iron precursors. X-ray diffraction (XRD) measurements indicated that FeS2 was the active species for SO2 hydrogenation. The proposed mechanism suggested that the best Fe/gamma-Al2O3 catalyst should have the best cooperation action between the hydrogenation function (FeS2 + H-2 = FeS + H2S) and the acidic catalytic function (H2S + 1/2(SO2) = 3/4(S-2) + H2O).