Two catalysts, MnOx and ceria modified MnOx were prepared by deposition-precipitation method and used for low-temperature selective catalytic reduction (SCR) with NH3 in the presence of SO2. The catalysts were characterized by X-ray diffraction (XRD), surface area measurement (BET) and thermal gravimetry analysis(TG). The deactivation of MnOx and MnOx-CeO2 by SO2 was observed during SCR process. It was found that the resistance to SO2 could be greatly enhanced for Ce modified MnOx. It was because that the formation of Mn(SO4)x was prevented and the depositions of (NH4)2SO4 and NH4HSO 4 were significantly inhibited with the doping of ceria.