A commercial V2O5-WO3/TiO2 catalyst was doped with various transition metals (Ce, Cu, Fe, Mn, Co, Ni and Cr) using an improved impregnation method. The NH3 oxidation properties of them were measured to screen appropriate doping components for removing the slip ammonia from SCR system. Among them, 1% Cu/SCR catalyst exhibited excellent selective catalytic oxidation (SCO) properties of NH3. Its NH3 removal efficiency and N-2 selectivity reached approximately 90% and 96%, respectively, in the simulated flue gas at the gas hourly space velocity (GHSV) of 7.5 x 10(4) h(-1). Besides, almost all the residual NO and about 90% of Hg-0 can be removed by it. Characterization results proved that the introduction of Cu had no significant effect on specific surface area and structure of SCR catalyst, but increased the acid sites and NH3 adsorption capacity. The deposited copper species mainly existed in the form of monomeric Cu2+ ions and small CuO clusters. The generated Cu2+ + V4+ <--> V5+ + Cu+ redox pair significantly increased the redox properties of the catalyst and may play a critical role in the SCO of slip ammonia. According to the in situ diffuse reflectance infrared spectroscopy (DRIFTS) results, more NH3 species were activated on the Cu/SCR catalyst and the NH3 oxidation follows an internal SCR (iSCR) mechanism.