In this study, we investigated the effect of potassium on the activity and regeneration of potassium-poisoned SCR catalysts. With the addition of potassium species, the NO conversion rate of the catalysts continuously decreased. After washing the poisoned catalysts with an H2SO4 solution or doping them with CeO2, the activity of the catalysts was improved to different extents. Acid washing almost completely removed the surface potassium species, freeing acidic sites to adsorb NH3, but it also potentially removed some of the active components, such as vanadia. CeO2 doping, on the other hand, added active components. Combining these two methods, the poisoned catalysts were washed with an H2SO4 solution and then doped with 5 wt.% CeO2. It was found that the level of activity could be restored to that of a fresh catalyst, and a conversion rate of over 90% was observed for NO between 300°C and 450°C, as the added CeO2 compensated for the active components lost during SCR reactions. Consequently, the above hybrid method shows high potential for regenerating commercial SCR catalysts.