Abstract: Alkali metals can poison denitrification catalysts and reduce the denitrification activity of the catalysts. In order to improve the stability and activity of VWTi catalysts in high alkali metal environments, this study was carried out to improve the performance of VWTi catalysts against alkali metal poisoning by doping with Sn element. VWTi catalysts with different Sn contents were successfully synthesised by the iso-volume impregnation method and their resistance to different alkali metals (KCl, K₂O, NaCl, Na₂O) was systematically evaluated. The catalysts were tested using characterisation tools such as X-ray diffraction (XRD), nitrogen adsorption-desorption (BET) and X-ray photoelectron spectroscopy (XPS). It was found that the addition of Sn effectively increased the acidic sites on the surface of the catalyst, significantly improving its resistance to alkali metal poisoning. In addition, Sn doping was found to increase the number of acidic sites and the total acid amount of the catalyst by ammonia programmed temperature rising desorption (NH₃-TPD) analysis. Hydrogen programmed temperature rising reduction (H₂-TPR) and XPS results showed that SnO₂ doping significantly improved the redox properties of the catalysts, increased the surface chemisorption of oxygen species and enhanced their selective catalytic efficiency for ammonia. The constructed quantum chemical models of catalysts and alkali metals were used to calculate the reactivity of various alkali metal poisons with catalysts based on the frontier orbital theory to reveal the chemical reaction mechanism between alkali metal poisons and catalysts, and the results showed that the reactivity of alkali metals with catalysts was in the order of NaCl>KCl>Na₂O>K₂O, indicating that NaCl was most likely to be chemically poisoned by combining with catalysts. The experimental results show that the degree of catalyst poisoning caused by different alkali metal species is KCl>K₂O>NaCl>Na₂O, indicating that KCl causes the most significant decrease in catalyst performance due to poisoning.Under the condition of high alkali metal concentration, the SnVWTi catalysts with 2% Sn doping showed excellent catalytic activity and stability. The performance against KCl poisoning at 300 ℃ was improved by 33.48% compared to the VWTi catalyst. This study summarises the mechanism of metal element doping on the performance enhancement of VWTi catalysts, which can help to deeply understand the modification of metal elements on the physicochemical properties of VWTi catalysts, and provide guidance and reference for the development of high-efficiency alkali metal poisoning-resistant VWTi denitrification catalysts, and the Sn-doped VWTi catalysts prepared with alkali metal poisoning have obvious improvement in the ability to resist alkali metal poisoning and have obvious advantages in the treatment of flue gas with high concentration of alkali metal.