Abstract: A series of Co-doped Mn oxide catalysts with different Co/Mn molar ratios were prepared by co-precipitation method, which was systematically characterized by XRD, SEM, H₂-TPR and NH₃-TPD etc. Co-doped Mn oxide catalysts are evaluated for NH₃-SCR activity and resistance to SO₂ and/or H₂O, and the Co(1)-MnO_x catalyst with Mn/Co molar ratio of 1∶1 performs the best catalytic performance, which achieved higher than 90% NO_x conversion in the temperature range of 100−275 °C and possessed better SO₂ and H₂O resistance. The Co(1)-MnO_x catalyst presented a sphere-like structure possessing a relatively large surface area. Doping of cobalt greatly improved the high-valent metal ions and chemisorbed oxygen content of Co(1)-MnO_x catalyst surface, and the catalyst possessed abundant active species and acid sites and apparent activation energy of the catalyst was reduced, which makes Co(1)-MnO_x a highly effective NH₃-SCR catalyst.