The effect of photoreduction on the properties of Pt/TiO 2 catalysts was investigated. A decrease of the white-line area in the XANES spectra of Pt/TiO 2 catalysts at the Pt L I I I edge was observed with increasing photoreduction time, which denoted the photoreduction of Pt/TiO 2 with UV illumination. From the EXAFS fitting results, the growth of Pt particles with the photoreduction time could be monitored. The XPS spectra of Pt/TiO 2 catalysts at the Pt 4f 5 / 2 and Pt 4f 7 / 2 bands showed the presence of Pt 0 and Pt 2 + states after photoreduction and the fraction of metallic Pt 0 was increased with increasing photoreduction time. The optimum photoreduction time for DCA (dichloroacetic acid) decomposition was 6 h. The partially reduced state of Pt seems to be effective to obtain a high quantum yield in DCA decomposition with minimizing the agglomeration of Pt clusters on the TiO 2 surface.