The mechanisms of sulfur dioxide poisoning on Mn/TiO2 and Mn-Ce/TiO2 catalysts are studied and poisoning resistance effect of cerium is revealed. Both two kinds of catalysts were deactivated to reduce NOx removal in the presence of SO2, however, the sulfur resistance performance of the Ce doping catalysts was obviously improved. From the result of DRIFT and DFT, SO2 can first adsorb on the manganese-terminal (Lewis acid sites) to form sulfates, which inhibit the adsorption of NH3 in the SCR reaction. Deactivation of Bronsted acid sites was due to the formation of bisulfite, which can react with NH4+ form NH4HSO4. For the Mn-Ce/TiO2 catalysts, SO2 preferentially adsorbed on Ce atom as sulfate species, alleviating the sulfation of the main active sites (Lewis acid sites and Broosted acid site on MnOx) under the effect of SO2. Furthermore, cerium sulfate can produce new Bronsted acid site and contribute to the low-temperature SCR processes. (C) 2016 Elsevier B.V. All rights reserved.