Abstract: The promotion effect of Ce modification on V₂O₅-WO₃/TiO₂ for the selective catalytic reduction (SCR) of NO_x with NH₃ and the SO₂ deactivation mechanism were investigated. Compared with V₁W₅Ti catalyst, the advantage of V₁W₅Ce₆Ti catalyst shows a good catalytic activity. These catalysts were investigated by means of XRD, BET, FT-IR, TG-DSC and XPS. The results demonstrate that the active components of V and W are well-dispersed, while a small cluster of cubic CeO₂ appears over the V₁W₅Ce₈Ti catalyst. The sulfation of V₁W₅Ti under reactive conditions can generate NH₄HSO₄ and (NH₄)₂SO₄ at 250℃. The Ce additive to V₁W₅Ti could provide stronger Brønsted acid sites and more chemisorbed oxygen. The deposited ammonium sulfate on V₁W₅Ce₆Ti catalyst is much smaller than that on V₁W₅Ti because the cerium sulfates species on the surface of V₁W₅Ce₆Ti is formed and the deposition of ammonium sulfate is inhibited, which can disrupt the redox cycle between Ce³⁺ and Ce⁴⁺ and break the V-O-Ce structure, causing the deactivation of V₁W₅Ce₆Ti catalyst.