Pt/Pt4+-TiO2　photocatalyst　prepared　by　a　modified　sol-gel　process　was　investigated　by　X-ray　diffraction,　UV-Vis　diffuse　reflectance　spectra,　X-ray　photoelectron　spectroscopy,　time-resolved　photoconductivity　and　terephthalic　acid　fluorescence　probing.　The　photocatalytic　activities　of　catalysts　were　evaluated　by　using　ethylene　oxidation　studies　under　visible　light　irradiation　(lambda＞450　nm)　from　40　to　62　degreesC.　It　is　found　that　the　platinum　doping　in　titania　caused　significant　absorption　shift　to　the　visible　region　and　the　surface　recombination　of　photogenerated　carriers　was　inhibited.　The　results　show　that　ethylene　was　not　converted　on　conventional　TiO2　while　the　conversion　was　90%　and　the　complete　mineralization　was　achieved　over　Pt-Pt4+/TiO2　at　62　degreesC　in　our　experiment.　Besides　the　exponential　increase　of　thermalcatalytic　activity,　pure　photocatalytic　activity　of　the　planitized　sample　enhanced　linearly　with　the　increase　of　temperature.