Abstract: Aiming at the problem of insufficient mercury oxidation in flue gas denitrification system of coal-fired power plants, a series of copper-modified attapulgite (Cu-ATP) catalysts were prepared, which were expected to achieve efficient oxidation of elemental mercury (Hg⁰) at the tail of denitrification equipment. The mercury oxidation activity of Cu-ATP was tested in the temperature range of 150~400℃. The effects of flue gas components including HCl, O₂, SO₂, H₂O and NH₃ were respectively investigated. Besides, the mercury oxidation performance was also studied in the simulated flue gas at tail of denitrification device. The results show that the presence of 8.1mg/m³ HCl could significantly improve the mercury oxidation activity of Cu-ATP catalysts. In the simulated flue gas, the mercury oxidation efficiency of Cu₃-ATP catalyst reached about 94%. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the catalysts, which found that the presence of surface CuO species may play an important role in mercury oxidation. According to the results, the formation of active chlorine and Cl₂ on the surface of Cu₃-ATP would promote the efficient oxidation of Hg⁰ in the presence of HCl and O₂. The existence of SO₂ could inhibit the formation of Cl₂, so the active chlorine plays a key role in the mercury oxidation reaction on the surface of Cu₃-ATP.