Abstract: The Cl-V₂O₅-WO₃/TiO₂ catalysts were prepared by impregnation methods. With the Cl ions content increased from 0 to 2.5%, the NO conversion of Cl-V₂O₅-WO₃/TiO₂ catalysts increased at first and then decreased. Combined with the experimental results, 1.5% Cl-V₂O₅-WO₃/TiO₂ catalyst was the optimal catalyst, NO conversion was higher than 95% in the range of 149-362℃, and NO conversion was higher than 90% in the temperature range of 145-385℃. The catalysts were characterized by XRF, BET, XRD, TG, FT-IR and H₂-TPR. The specific surface area and pore volume of the catalysts decreased in different degrees after adding SO₂ and H₂O in reactant gas. The poisoned catalysts deposited sulfur species and contained NH₄⁺ and SO₄^2-. Adding appropriate amount of Cl ions inhibited the formation of side byproducts and enhanced the poisoning resistance of V₂O₅-WO₃/TiO₂ catalyst.