Nanometer sized Au/TiO2 particles were synthesized by irradiation of a HAuCl4 solution containing colloidal TiO2 with light of wavelength (lambda) >330 nm. The absorption maximum attributed to the surface plasmon band of gold was observed at 530 nm, a red shift of about 10 nm from the position in aqueous solution, The particle size of Au/TiO2 determined by TEM was about 25 nm. The Au clusters are situated on the surface of TiO2 in terms of microcrystallite, which was confirmed by HRTEM, EDS, and XRD, A negative shift of binding energy in the Au 4f(7/2) for gold cluster an the surface of TiO2 was found, and the electronic interaction between the metal and the support was discussed.