Cr8Cu2Mnx/FA catalyst was prepared by the ultrasonic-assisted impregnation method using coal-based fly ash as the catalyst carrier, Cr2O3 as the main active component, and CuO and Mn2O3 as the metal additives. The SCR denitration experiments were carried out. The effects of Mn doping on thedenitrification activity and steam-resistance of Cr-based catalysts were studied. The catalysts were characterized using BET, XRD, TPD, TPR and XPS analysis. The results showed that Mn doping could widen the temperature window of the denitrification activity of the Cr-based catalyst. Also, Cr8Cu2Mnx/FA catalyst achieved a denitrification efficiency of 100% within the temperature range of 200~350 ℃ and had a good steam-resistance. The proper addition of Mn could improved the surface acidity, redox capacity, and adsorbed oxygen content on the catalyst surface, enlarged the denitrification temperature window of the catalyst and promoted the electron transfer of active metal components (Cr and Cu) ( Cr5+→Cr3+→Cr2+, Cu+→Cu2+) .