Abstract: The massive emission of nitrogen oxides has caused serious harm to the environment and human beings, but the treatment technology of nitrogen oxides in the low-temperature flue gas still needs to be developed urgently. In this study, Mn-doped CeTiO_x (MnCeTiO_x) catalysts were synthesized by a simple co-precipitation method, which was adopted as catalysts for NO oxidation to NO₂ by ozone and hydrogen peroxide at low temperature, so as to achieve synchronous desulfurization and denitrification in the following steps. The results show that after Mn doping, the electron synergism between Mn, Ce and Ti enhances the surface oxidation-reduction property of catalyst, which could promote the activation of O₃ and H₂O₂ to free radicals on catalyst surface, thereby enhancing the catalytic activity for converting NO to NO₂. When the concentration ratio of O₃ to NO is set to 0.4, and that of H₂O₂ to NO is 0.8, 83% of NO could be oxidized to NO₂ on Mn_0.25CeTiO_x catalyst at 140 ℃.