Palladium supported by Ce0.7Sn0.3O2 has been prepared by an impregnation method, and used for low temperature carbon monoxide oxidation. They were characterized by means of XRD and H-2-TPR techniques. For PdO/Ce0.7Sn0.3O2 catalyst, three reduction peaks (alpha, beta and gamma) are observed. The alpha peak contributes to the reduction of PdO species and Sn4+ species on the surface of Ce0.7Sn0.3O2; the beta peak to the reduction of bulk SnO2 and surface Ce4+ and the gamma peak to the reduction of bulk CeO2. The increase of Pd loading from 0 to 0.75% enhances oxidation of CO, further increase of the Pd content affects the catalytic activity but slightly. XRD and TPR results show that highly dispersed Pd on the surface of the support is the active species for CO oxidation.