In order to study the combined deactivating effect of alkaline metals on commercial SCR catalyst, we detected the catalytic performances when potassium and calcium exist simultaneously in flue gas with different proportions. After preparing V/Ti catalyst by the wetness impregnation method, we coated potassium and calcium with different concentrations. The results showed catalysts coated with alkaline metals present an obvious deactivation by contrasting the catalyst performance of VK0Ca0 from 250 °C to 350 °C. But it seems that there is no obvious relationship between the catalyst performance and the proportions of K2O and CaO. Furthermore, BET, XRD, SEM and EDS were performed to investigate the physical property, crystal phases, surface morphology and chemical composition, respectively.