A series of modified gamma-Al2O3 supported iron-based catalysts (M-Fe/gamma-Al2O3) was developed to reduce SO2 in actual smelter off-gases using CO-H-2 gas mixture as reducing agent for sulfur production. Used as modifiers, three metal additives - Ni, Co, and Ce were added to Fe/gamma-Al2O3 catalysts. Changes in catalyst structure and active phase were characterized with X-ray diffraction, XPS, SEM, and EDS. The reduction ability of catalysts was exhibited via CO-TPR. The prepared catalysts only need to be pre-reacted for a period of time, eliminating the need for presulfidation treatment. Reaction conditions were optimized in a fixed bed reactor to achieve high SO2 conversion and sulfur selectivity. XRD characterization was carried out to verify the resulting sulfur products. Combining in situ infrared characterization and catalyst evaluation of support and active component, the reaction mechanism was investigated and proposed. (c) 2018 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.