The Ce 0.75 Zr 0.25 O 2 -supported Pt catalysts with different Pt loadings were prepared by the impregnation method. The results of isotopic exchange of 18 O, temperature-programmed surface reaction of ethanol (C 2 H 5 OH-TPSR), temperature-programmed desorption of CO (CO-TPD), and temperature-programmed reduction of H 2 (H 2 -TPR) show that the Pt phase is amorphous and well dispersed on the support surface. The C 2 H 5 OH-TPSR and CO-TPD results show a good correlation of the amount of desorbed CO 2 with the catalytic activity for ethanol or CO oxidation. The Pt/Ce 0.75 Zr 0.25 O 2 catalyst has improved activity for ethanol or CO oxidation, and the catalytic activity is related to the Pt loading. The results of the ethanol or CO oxidation and isotopic exchange of 18 O 2 show that the oxygen exchange capacity is responsible for the improved catalytic activity. The sample with the best catalytic activity has the highest surface oxygen diffusion rate.