Display omitted •Pr-modified MnCeOx catalysts exhibited excellent SCR performance and SO2 tolerance.•The SCR reaction pathways based on both L-H and E-R mechanisms were investigated.•The ad-NH3 species on MnCePrOx-0.3 showed superior reactivity.•Abundant of Oads and Mn4+ on MnCePrOx-0.3 catalysts promoted the “fast SCR”. Using a one-step impregnation method, a series of Pr-modified MnCeOx catalysts with different Pr molar ratios were created to manufacture an efficient and effective catalyst for low-temperature NH3-SCR. It was demonstrated that the Pr modification could extensively boost the MnCeOx catalysts’ de-NOx activity and SO2 resistance and led to the formation of a unique broom-like morphology, especially when the molar ratio of Pr/Mn = 0.3, the MnCePrOx-0.3 exhibited above 90 % NO conversion at 250 °C with the existence of 100 ppm SO2. According to the characterization results, the enhancement of Pr doping for MnCeOx catalysts was mainly manifested by the expanded specific surface area, the improved dispersion of active components, the enhanced surface acidity and redox ability, and the generated more chemisorbed oxygen (Oads) species. All these characteristics allowed the NH3-SCR reaction over MnCePrOx-0.3 catalysts to proceed through the both Eley-Rideal (E-R) and Langmuir-hinshelwood (L-H) mechanism.