Several MnFe-based multi-metal oxides were synthesized as NH3-SCR catalysts by a simple coprecipitationmethod for abating NOx of marine diesel exhausts. The Co and Nb-doped MnFeCeAl catalysts exhibitNOx conversion over 90% and N2 selectivity above 95% at 180–270 C, especially the MnFeCeAlCo catalystscan inhibit nearly all sulfate species growth within 150 ppm humid-SO2 gases at 225 C. The structuralcharacterization results revealed that Co, Nb, Sm, and Sb doping can enhance interactions amongdifferent components and promote active component dispersion. Temperature programmed analysisindicated that the Co doping is not only more favorable for improving redox properties, but can alsoenhance the surface acidity, which are advantageous to improve the activity, N2 selectivity, andhumid-SO2 resistance. Moreover, the XPS results implied that the binding energy shift or the valence variationof the Sm, Sb, Nb, and Co species on catalyst surfaces are favored to raise the atomic ratios of highvalentMn species and surface adsorbed oxygen, which can promote the redox property significantly andfurther facilitate SCR activity. Accordingly, the excellent activity and humid-SO2 tolerance of theMnFeCeAlCo catalyst should attribute to its lower redox temperature, strong interaction between oxides,47.3% surface Mn4+/Mn3+ species, and 71.8% adsorbed oxygen, which provide a method for improving theSCR performances of MnFe-based catalysts with humid SO2 resistance.