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.