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In this study, Al 2 O 3 , ZrO 2 , La 2 O 3 , and Y 2 O 3 were separately introduced into Pt/CeO 2 -MnO x catalyst to improve the thermal stability of catalysts and obtain a better soot and NO oxidation activity after thermal treatment. CeO 2 -MnO x -RO x (R = Al, La, Y, or Zr) mixed oxides were prepared by a co-precipitation method. The catalysts were characterized by XRD, BET, H 2 -TPR, CO chemisorption, XPS, TG analysis, soot–TPO, and NO–TPO. It is found that the introduction of R n + into CeO 2 -MnO x markedly increases the thermal stability of the catalysts for soot and NO oxidation, remaining a better catalytic oxidation activity. On the one hand, after high-temperature aging, for the modified catalyst Pt/CeMnRO x , the ignition temperature of soot oxidation ( T i ) and maximal soot oxidation rate temperature ( T m ) increase by 30–50 °C and 4–32 °C, respectively, whereas Al 3 + -modified catalyst shows the best thermal stability. On the other hand, due to a key role of NO 2 as a strong oxidizing agent in soot oxidation process, the NO oxidation activity is often considered as an important aspect. This work shows that R n + -modified catalysts display a better stability on NO oxidation activity after aging. Some factors leading to the thermal deactivation of catalysts are also discussed in this paper. [ABSTRACT FROM AUTHOR]