Low-temperature activity and SO2 poisoning were the key factors limiting the application of NH3-SCR catalysts.In this study, Fe2(SO4)3/AC and Fe2(SO4)3/OAC catalysts were prepared by oxidation function modification and incipient wetness impregnation.In the temperature range of 100-250°, the catalytic performance and SO2 resistance of Fe2(SO4)3/AC and Fe2(SO4)3/OAC catalysts were investigated, the denitrification efficiency increased from 28% (Fe2(SO4)3/AC) to 80% at 100° and reached 100% at 170°, and 100 ppm SO2 was introduced at 250° for 24 h, the denitrification efficiency remains 100% unchanged.The mechanism of activity enhancement was further explored by BET, x-ray diffraction, ICP, TG, XPS, FT-IR, H2-TPR and NH3-TPD.(NH4)2S2O8 modification enhanced the surface acidity, and the increase of surface oxygen-containing functional groups improved the redox performance.At the same time, due to electrostatic anchoring effects of oxygen-containing functional groups, Fe3+ and SO2-4 were adsorbed at different sites and promoted the binding of S to the carbon skeleton to form -C-S-C-.Thus, the interaction between OAC and Fe2(SO4)3 caused part of Fe2(SO4)3 to decompose into Fe2O3, and the formation of Fe2(SO4)3-Fe2O3 interface further enhanced the acidity and redox properties.More importantly, the decomposition temperature of NH4HSO4 was lower and the decomposition was more thorough on the Fe2(SO4)3/OAC than that of Fe2(SO4)3/AC.Finally, the possible mechanism of (NH4)2S2O8-modified Fe2(SO4)3/OAC catalyst to improve NH3-SCR performance was proposed, which is of great significance for the development of NH3-SCR catalyst with sulfur resistance at low temperatures