Abstract: The nano TiO₂/ceramic supported V₂O₅-WO₃ catalysts (V₂O₅-WO₃/TiO₂(C)) were prepared. Their poisoning by alkali metal (K, Na) impregnated and regeneration were investigated. The catalysts were characterized by XRD, FT-IR, H₂-TPR, XPS measurements. The results indicated that the catalytic activity is decreased by adding alkali metals; potassium is more poisonous than sodium. FT-IR results suggested that Lewis acid sites in the catalysts are active in the de-NO_x reaction. H₂-TPR and XPS analysis revealed that potassium leads to a decrease of the surface redox ability, which may reduce the oxygen adsorption and the SCR activity of the catalyst. Washing with water can not get back the catalyst activity, suggesting that potassium is not physically deposited on the catalyst surface. The activity of the poisoned catalysts can be well regenerated by washing with sulfuric acid at high temperature.