Using vanadium-tungsten-titanium catalyst can effectively reduce NO and dioxin in sintering flue gas, while potassium salt contained in the flue gas will reduce the activity of the catalyst. In this study, the fresh vanadium-tungsten-titanium catalyst was deactivated by wet impregnation method in the laboratory. The effects of three potassium salts (K2SO4, K2O, and KCl) loaded on the surface of the catalyst on its denitration and dioxin removal activities were investigated. The regeneration performance of the deactivated catalyst was studied by water washing and acid pickling process. The results confirmed that the activities of denitration and dioxin removal were reduced by different potassium salts, and the order of reduction are following the sequence: KCl> K2O> K2SO4. The deactivation mechanism of catalyst mainly includes physical deactivation and chemical deactivation. Physical deactivation is mainly caused by the deposition of potassium salts on the surface of the catalyst and blocking its pores. The chemical deactivation mainly refers to the interaction between the potassium salts and the active component on the catalyst surface, which inactivates the surface active site, weakens its oxidation reducibility, and reduces the number of acid sites on the surface, thereby decreasing the denitration and dioxin removal activities of the catalyst. The regeneration experiment results showed that water washing could restore the denitration activity of the catalyst; acid pickling would lead to the loss of active substances on the surface of the catalyst. However, neither water washing nor acid pickling could effectively restore the dioxin removal activity of the catalyst. Finally, the poisoning mechanism of different potassium salts on vanadium-tungsten-titanium catalyst was proposed.