The Ce 0.8 Y 0.2 O 1.9 solid solution was prepared by nitrate sol–gel method, and a series of catalysts with different PdO loading were prepared using impregnation method. These catalysts were characterized by XRD, Raman, CO-TPR, CO 2 - and O 2 -TPD techniques. The PdO is highly dispersed on the surface of the solid solution when the loading is lower than 0.5wt.%. As PdO loading increases to 2wt.%, it begins to form the crystalline structure. CO 2 -TPD profiles show that the CO adsorbed on highly dispersed PdO is more easily oxidized to CO 2 than that adsorbed on crystalline structure and O 2 -TPD results indicate that it is more difficult to decompose for highly dispersed PdO than that for crystalline structure. CO-TPR profiles show that the highly dispersed PdO is easily reduced. Catalytic activities of these catalysts for CO and CH 4 oxidation indicate that both the highly dispersed and crystalline PdO are the active site for CO oxidation, while the crystalline structure is the active site for CH 4 oxidation.