Catalyst addition can improve system after treatment efficiency of pollutants purification. In this study, the performance of (Mn, Hf) co-doped Ce-based catalysts has been investigated in oxidation to mitigate CO emission of engines. A series of Ce-Mn-Hf-Ox with different metal ratios (Ce: Mn: Hf = 8:1:1,7:2:1,7:1:2,6:1:3,6:2:2 and 6:3:1) catalysts were prepared. DFT (density functional theory) calculations were carried out to investigate the mechanism of applied surface catalytic reaction. XRD (X-ray Diffraction) analysis and SEM (Scanning Electron Microscope) revealed Mn and Hf doping increased the catalysts surface area contact with the CO gas with the catalytic performance improvement. XPS (X-ray Photoelectron Spectra), H2-TPR (Temperature-Programmed Reduction) and DFT calculations manifested the Mn and Hf doping would promote the formation of oxygen vacancy to enhance the catalytic performance for CO oxidation. The thermal stability of the catalysts increased with Hf content increasement. Ce6Mn3Hf1 had the highest catalytic activity with the favorable thermal stability according to the temperature-programmed oxidation of CO experiment. T10, T50 and T90 of CO oxidation were 156, 188 and 198 °C, which lost 4.82 % mass at 500°C and 6.18 % mass at 900 °C. Ce6Mn1Hf3Ox displayed the best thermal stability according to TG with the lowest catalytic activity.