The effect of different potassium species, including K2O, KCl and K2SO4, on the deactivation of V2O5-WO3/TiO2 catalysts were measured in the research. Potassium species were supplied by impregnating catalyst with corresponding KNO3, KCl and K2SO4 aqueous solution. Catalytic activity was also measured and the physical and chemical properties of fresh and poisoned catalysts were characterized by XRD, N-2 physisorption, NH3-TPD, H-2-TPR, XPS and NH3-DRIFTS. Deactivation could be observed in the potassium-containing catalysts and the deactivation rate follows KCl > K2O > K2SO4. The surface chemisorbed oxygen was also reduced and the downward trend was in good accordance with the SCR activity. In addition, both the amount and stability of the Bronsted and Lewis acid sites dropped after potassium introduction, and the reducibility of surface active species decreased. The introduction of SO42- created new Bronsted acid sites and performed advantages to ammonia adsorption and NO reduction. Cl-could react with vanadia active sites to form -O-V-Cl bond, which provided some new ammonia adsorption sites, but these newly generated sites could not revitalize the adsorbed ammonia and were helpless to catalytic activity promotion. Besides, KCl presented the maximum impact on catalyst reducibility was another contribution to its largest activity decline. Finally, the probable poisoning mechanisms of different potassium species over V2O5-WO3/TiO2 catalysts were proposed.