A series of catalysts of Mn/USY and Mn-Fe/USY prepared by impregnation were studied for low-temperature selective catalytic reduction (SCR) of NO with NH3 in the presence of excess of oxygen. It was found that the addition of Fe enhanced the catalytic performance at low-temperature. Mn-Fe/USY catalyst yielded nearly 100% NO conversion in a range of temperature from 423 to 573 K at a space velocity of 36 000 cm3.g-1.h-1. Coexistence of manganese and iron oxides enhanced the dispersion of the supported oxides,no visible phase of the oxides can be observed on catalyst. The addition of Fe enhanced the number and strength of the Brnsted and Lewis acid sites on the surface of the catalyst,which might promote the absorption of NH3 to form active intermediate and enhance the catalytic performance at low-temperature. A series of catalysts of Mn / USY and Mn-Fe / USY prepared by impregnation were studied for low-temperature selective catalytic reduction (SCR) of NO with NH3 in the presence of excess of oxygen. It was found that the addition of Fe enhanced The catalytic performance at low-temperature. Mn-Fe / USY catalyst yielded nearly 100% NO conversion in a range of temperature from 423 to 573 K at a space velocity of 36 000 cm3.g-1.h-1. Coexistence of manganese and iron oxides enhanced the dispersion of the supported oxides, no visible phase of the oxides can be observed on catalyst. The addition of Fe enhanced the number and strength of the Brnsted and Lewis acid sites on the surface of the catalyst, which might promote the absorption of NH3 to form active intermediate and enhance the catalytic performance at low-temperature.