Display omitted •Excellent de-NOx catalysts based on Mn-Ce mixed-oxide were developed.•The Mn-Ce mixed-oxide catalyst exhibited unusual positive effects of SO2.•The interaction between SO2 and Ce enhanced NO adsorption and oxidization. A high-performance denitration catalyst based on Mn-Ce mixed-oxide derived from a specific Mn/Ce precursorwas fabricated by solvothermal method. It exhibited outstanding low-temperature activity, which achieved above 90% NOx conversion in the temperature of 150–310 °C. Remarkably, Mn-Ce mixed-oxide demonstrated a much better SO2 tolerance, in which the NOx conversion increased from 92.6% to 97.8% at 150 °C after introducing 200 ppm SO2. The synthesized Mn-Ce mixed-oxide has a porous structure with abundant chemisorbed oxygen spices and exposed active sites. In addition, the increased acidity and redox capacity enhanced the catalytic activity after introducing SO2. Meanwhile, the injection of SO2 separates NH3 adsorption sites from oxidation agents, inhibiting the unwanted oxidization of ammonia to nitrogen oxides. Furthermore, the reaction pathway on Mn-Ce mixed-oxide proved to be the L-H mechanism based on in situ DRIFTS. Thus, the synthesized Mn-Ce mixed oxide demonstrated an excellent denitration performance and the especially high SO2 tolerance, showing great potential for low-temperature NH3-SCR.