To characterize the oxygen mobility over metal supported catalysts on a dynamic and in situ base, O-18/O-16 isotopic exchange reaction combined with CO oxidation was designed and exemplified on three kinds of three way catalysts of Pt/CeO2-ZrO2 (CZ-O, CZ-D and CZ-R). The obtained oxygen diffusion coefficients, oxygen release rate, and oxygen storage capacity were discussed and correlated with XRD spectra and other physical parameters. It was found that the oxygen mobility and oxygen storage capacity were parallel to the structural homogeneity of Zr introduction into the CeO2 frame work, and decreased as: CZ-R > CZ-D > CZ-O. These results indicated that this combined isotopic exchange technique could be used to quantify the surface and bulk oxygen mobility, the oxygen storage capacity and oxygen release rate over the metal supported catalysts, and could be employed as a meaningful probe into the nature of CeO2-ZrO2 oxygen storage material. The oxygen mobility is also another important indicator for the development of oxygen storage materials. (C) 2004 Elsevier B.V. All rights reserved.