Co-doping of silver and manganese ions in ceria was found to be an effective method for enhancing the oxidative reactivity of soot combustion. Several Ag-MnxCe1-xOy catalysts were prepared through the facile co-precipitation method, which exhibited a T-m in the range of 321-370 degrees C in loose contact conditions, much lower than the generally required similar to 600 degrees C. Characterizations of XRD, XPS, Raman, H-2/O-2 pulse reaction, H-2-TPR and O-2-TPD revealed increased oxygen defects and improved catalytic performance of Ag-MnxCe1-xOy for soot combustion due to incorporation of Ag+ and Mn delta(+) in the solid solutions. The effective co-doping of silver and manganese in ceria was achieved at an optimal ratio of x = 0.1, which facilitates the formation of Ag+ with a new structure that delivers extra oxygen vacancies with enhanced oxygen mobility. The Ag-Mn0.1Ce0.90Oy, showed a minimum T-m of 321 degrees C with superior stability in repeated soot oxidation tests among all the Ag-MnxCe1-xOy catalysts prepared. It was hypothesized that the enhanced redox property of ceria by the co-doping of Ag and Mn is responsible for the excellent performance of the Ag-MnxCe1-xOy type catalysts.