Abstract: To enhance the catalytic combustion efficiency of diesel soot particles, the oxygen vacancy structure of Mn-Ce catalysts was modulated via silver （Ag） doping, and its effect on soot combustion performance was investigated. MnO_x-CeO₂ composite catalysts with different Mn-to-Ce ratios （Mn_xCe_y） were prepared using the co-precipitation method, followed by loading 3% mass percentage of Ag via impregnation. Through characterization of the physicochemical properties of the catalysts and temperature-programmed oxidation experiments, the catalytic performance for soot oxidation was analyzed. The results showed that after Ag loading, the Mn₃₃Ce₆₆Ag catalyst exhibited a lower ignition temperature （T₁₀=287 ℃） and a lower complete combustion temperature （T₉₀=332 ℃）, along with excellent cyclic stability, as T₉₀ only increased to 386 ℃ after three cycles. Characterization analysis results show that Ag doping stabilizes Ce³⁺ through electron injection, increases the molar ratio of surface active oxygen species, and optimizes the oxygen vacancy concentration. Through H₂ temperature-programmed reduction, it is verified that Ag significantly reduces the surface oxygen reduction temperature （the main reduction peak of Mn₂₀Ce₈₀Ag shifted from 354.2 ℃ to 282.2 ℃）, accelerates oxygen activation, and enhances reducibility. The results demonstrate that the synergy between Mn⁴⁺ and Ce³⁺ promotes the activation of NO/O₂, while Ag improves stability by inhibiting CeO₂ grain growth and enhancing metal−support interactions.