The effect of CeO2 doping on structure and catalytic performance of Co3O4 catalyst was studied for low-temperature CO oxidation. The Co3O4 catalyst was prepared by a precipitation method and the CeO2/Co3O4 catalyst was prepared by an impregnation method. Their catalytic performance had been studied with a continuous flowing micro-reactor. The results reveal that the CeO2/Co3O4 catalyst exhibits much better resistance to water vapor poisoning than the Co3O4 catalyst for CO oxidation. The CeO2/Co3O4 catalyst can maintain CO complete conversion at least 8,400 min at 110 degrees C with 0.6% water vapor in the feed gas, while the Co3O4 catalyst can maintain at 100% for only 100 min. Characterizations with XRD, TEM and TPR suggest that the CeO2/Co3O4 catalyst possesses higher dispersion degree, smaller particles and larger S-BET, due to the doping of Ceria, and exists the interaction between CeO2 and Co3O4, which may contribute to the excellent water resistance for low-temperature CO oxidation. Furthermore, the H-2 detected in the reactor outlet gas seems to indicate that the water-gas shift reaction is the more direct reason.