In this study, we investigated the effect of potassium on the activity of the SCR catalysts and the regeneration of potassium-poisoned SCR catalysts. Given the addition of potassium species, NO conversion of catalysts continuously decreased. After washing with H2SO4 solution or addition of CeO2, activities of poisoned catalysts were improved to different extents. For acid washing, surface potassium species were almost completely removed, which made occupied acidic sites be released for the adsorption of NH3. However, acid washing may also remove part of active components such as vanadia. For CeO2 doping, extra active components were added. Combined with these two methods, poisoned catalysts were washed with H2SO4 solution and then doped with 5 wt.% CeO2. It was found that the activity could be restored to the level of the fresh one and over 90% NO conversion could be observed between 300 and 450°C. This is because added CeO2 compensated the lost active components for the SCR reactions. Consequently, the above hybrid method showed potential application in the regeneration of commercial SCR catalysts.