A series of S, P, Si?doped TiO₂ supports and the corresponding VO_x/TiO₂ catalysts were prepared by sol?gel method and impregnation method for the purpose of enhancing SCR performance.Among them,the S?doped VO_x/TiO₂ catalyst exhibited the best low and medium temperature SCR performance and the widest active temperature window.According to the results of various analyses,the doping greatly influenced the agglomeration of vanadium species.As a result, numerous active polymeric VO_x species were emerged on the surface of catalysts.Meanwhile,S and Si was doped into TiO₂ lattice via the replacement of Ti⁴⁺ by S⁴⁺ and Si⁴⁺ to generate Ti-O-S and Ti-O-Si bonds,along with producing more surface V⁴⁺+V³⁺ and more chemisorbed oxygen species.The synergistic effect of the two active species can promote the oxidation of NO to NO₂,which can participate in the fast?SCR reaction by accelerating the reoxidation of VO_x species in the Redox process,and then improve the SCR performance of VO_x/TiO₂ catalyst at low and medium temperature range.The redox ability and activity of P?doped VO_x/TiO₂ catalyst are relatively low,because more phosphate is produced in the catalyst.Although doping S,P and Si has a significant effect on the acidity of the catalyst,it is not the dominate factor to determine the SCR activity.