The catalytic oxidation of CO over Au/TiO2 in an H-2-rich stream was performed under UV irradiation. It is round that UV it radiation over Au/TiO2 promotes the preferential oxidation of CO in the H-2-rich stream. The respective chemisorption of CO, H-2 and O-2 at Au/TiO2 can be described as a process of forming -OH or H2O species. UV irradiation over Au/TiO2 enhances the chemisorption of CO but suppresses the chemisorption of H-2 both at TiO2 and Au surface. It is proposed that the photogenerated electrons from TiO2 will cause the change of the chemisorption of CO, H-2 and O-2 at Au/TiO2, which promotes the preferential oxidation of CO in an H-2-rich stream. (C) 2008 Elsevier B.V. All rights reserved.