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Direct decomposition of NO into N₂ and O₂ is an ideal technology for NO_x removal. Catalyst deactivation by sulfur poisoning is the major obstacle for practical application. This paper focuses on strengthening the SO₂ resistance of metal-exchanged HZSM-5 catalysts, by investigating the metals, promoters, preparation methods, metal-to-promoter molar ratios, Si/Al ratios and metal loadings. The results show that in the presence of SO₂ (500 ppm), Fe is the best compared with Co, Ni and Cu. Cs, Ba and K modification enhanced the low-temperature activity of the Fe-HZSM-5 catalyst for NO decomposition, which can be further improved by increasing the exchanged-solution concentration and Fe/Cs molar ratio or decreasing the Si/Al molar ratio. Interestingly, Cs-doped Fe-HZSM-5 exhibited a high NO conversion and low NO₂ selectivity but a high SO₂ conversion within 10 h of continuous operation. This indicates that Cs-Fe-HZSM-5 has a relatively high SO₂ resistance. Combining the characterization results, including N₂ physisorption, XRD, ICP, XRF, UV–Vis, XPS, NO/SO₂-TPD, H₂-TPR and HAADF-STEM, SO₄²⁻ was found to be the major sulfur species deposited on the catalyst’s surface. Cs doping inhibited the SO₂ adsorption on Fe-HZSM-5, enhanced the Fe dispersion and increased the isolated Fe and Fe-O-Fe species. These findings could be the primary reasons for the high activity and SO₂ resistance of Cs-Fe-HZSM-5.