The effect of photocatalytic activity of CO oxidation on Pt/TiO2 catalysts under oxidizing atmosphere was investigated. A strong metal-support interaction (SMSI) between Pt and TiO2 have been found by means of XPS and in situ Ar+ sputtering test after Pt/TiO2 films being calcinated at 673 K under oxygen for 2 h, which was also corroborated by the photoelectrochemical measurement. When Pt/TiO2 catalysts were calcinated at 673 K in air, the SMSI between Pt and TiO2 occurred. Pt atoms on the surface thermally diffuse into the lattice of TiO2 grains, and then the contact resistance on the interface decreases. The migration velocity of the photo-generated electrons from the surface of TiO2 to Pt particles increases, which may bring out the enhancement of the photocatalytic activity of CO oxidation. (c) 2006 Elsevier B.V. All rights reserved.