Titania-supported gold catalysts (Au/TiO2) prepared by the ionized cluster beam (ICE) method have been studied by STM, TEM, X-ray diffraction and assessed for their catalytic activity with the oxidation of CO. The temperature dependence of the CO oxidation for Au/TiO2 catalysts indicated that the catalytic activity was enhanced both by using anatase type of TiO2 supports and by depositing Au at an accelerating potential of 3 kV. For CO oxidation, O-2 molecules, absorbed on the TiO2 supports, migrate and react with CO molecules at the edge of the nano-scale Au islands. The enhancement of CO oxidation is due to the increase of absorption and migration for these O-2 and CO molecules. Thus, high activity of Au/TiO2 catalysts with good thermal stability can be obtained.