Abstract: A series of nanorod CeO₂(x)-NiO composite oxides catalysts with different Ce/Ni molar ratios have been synthesized by hydrothermal method. Their morphology and structure were characterized by N₂ sorption-desorption, XRD, TEM, Raman spectra, H₂-TPR and XPS. The effects of Ce/Ni molar ratio on the morphology and catalytic activity of CeO₂(x)-NiO composite oxides catalysts for CO preferential oxidation (CO PROX) in hydrogen-rich stream were studied. TEM results indicate that nanorod CeO₂(x)-NiO composite oxides catalysts with different sizes can be obtained by adjusting Ce/Ni molar ratio. H₂-TPR results show that introduction of NiO into CeO₂ enhance the redox ability of CeO₂(x)-NiO composite oxides catalysts. Raman spectra and XPS results indicate that CeO₂(x)-NiO composite oxides catalysts with low nickel content have much more active oxygen species and oxygen vacancies, which are beneficial to improve its catalytic performance. CeO₂(0.89)-NiO nanorod catalysts with low nickel content exhibits the highest activity and CO₂ selectivity, the CO conversion is 100% and the CO₂ selectivity is about 52% in the reaction temperature range of 170-220 ℃ for CO PROX in hydrogen-rich stream.