Abstract: A series of ceria oxide catalysts doped with Fe, Ni and Cu were prepared by hydrothermal method and they characterized by N₂ sorption, XRD, H₂-TPR, Raman spectra and XPS; the relationship between the structure of Ce-M mixed oxides and their catalytic performance in low temperature CO oxidation were then investigated. The results reveal that the incorporation of Fe, Ni and Cu metal ions into CeO₂ can remarkably increase the amount of oxygen vacancies in the doped samples, which is beneficial to the migration of the lattice oxygen; as a result, the doped Ce-M mixed oxides exhibit much higher reducibility and catalytic activity than the pure CeO₂. Among them, the CeCu catalyst with most oxygen vacancies exhibits the highest activity in CO oxidation, with a complete CO conversion at 130℃; over CeNi catalyst, in the next, a complete CO conversion is obtained at 180℃. On the contrary, CeFe catalyst is least active and the conversion of CO is only 92% at 200℃.