Abstract: The oxidation activity of elemental mercury (Hg⁰) by transition metal modified SCR catalysts was investigated by using the simulated SCR reactor. The physical and chemical properties of the catalysts were characterized by N₂ adsorption-desorption and X-ray diffraction (XRD). The results show that the specific surface area and total pore volume of the catalysts are decreased after the modification by metal oxide. However, the pore structure and distribution after modification have little variation. The weak diffraction peaks of transition metal oxide can be seen from the XRD pattern. Both 8% Ce/SCR and 8% Cu/SCR catalysts show a relatively stable and high Hg⁰ oxidation efficiency, while the oxidation activity of the 8% Co/SCR catalyst is greatly influenced by temperature. The modified SCR catalysts have an excellent catalytic performance for the Hg⁰ oxidation under a lower concentration of NH₃ and NO. And the Hg⁰ oxidation efficiency is promoted significantly in the presence of HCl. On the contrary, there is little improvement in the Hg⁰ oxidation by HCl at the condition of higher concentration of NH₃ and NO.