A series of Au catalysts supported on CeO2-TiO2 with various CeO2 contents were prepared. CeO2-TiO2 was prepared by incipient-wetness impregnation with aqueous solution of Ce(NO3)(3) on TiO2. Gold catalysts were prepared by deposition-precipitation method at pH 7 and 65 degrees C. The catalysts were characterized by XRD, TEM and XPS. The preferential oxidation of CO in hydrogen stream was carried out in a fixed bed reactor. The catalyst mainly had metallic gold species and small amount of oxidic Au species. The average gold particle size was 2.5 nm. Adding suitable amount of CeO2 on Au/TiO2 catalyst could enhance CO oxidation and suppress H-2 oxidation at high reaction temperature (>50 degrees C). Additives such as La2O3, Co3O4 and CuO were added to Au/CeO2-TiO2 catalyst and tested for the preferential oxidation of CO in hydrogen stream. The addition of CuO on Au/CeO2-TiO2 catalyst increased the CO conversion and CO selectivity effectively. Au/CuO-CeO2-TiO2 with molar ratio of Cu:Ce:Ti = 0.5:1:9 demonstrated very high CO conversion when the temperature was higher than 65 degrees C and the CO selectivity also improved substantially. Thus the additive CuO along with the promoter and amorphous oxide ceria and titania not only enhances the electronic interaction, but also stabilizes the nanosize gold particles and thereby enhancing the catalytic activity for PROX reaction to a greater extent. Crown Copyright (C) 2009 Published by Elsevier Ltd on behalf of International Association for Hydrogen Energy. All rights reserved.