The　catalytic　oxidation　of　CO　over　Au/TiO2　in　an　H2-rich　stream　was　performed　under　UV　irradiation.　It　is　found　that　UV　irradiation　over　Au/TiO2　promotes　the　preferential　oxidation　of　CO　in　the　H2-rich　stream.　The　respective　chemisorption　of　CO,　H2　and　O2　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　H2　both　at　TiO2　and　Au　surface.　It　is　proposed　that　the　photogenerated　electrons　from　TiO2　will　cause　the　change　of　the　chemisorption　of　CO,　H2　and　O2　at　Au/TiO2,　which　promotes　the　preferential　oxidation　of　CO　in　an　H2-rich　stream.　©　2008　Elsevier　B.V.　All　rights　reserved.