Pt-loaded TiO2 (Pt/TiO2) catalysts for photocatalytic water splitting were prepared by the polygonal barrelsputtering method. The results showed that the evolution rates of H-2 and O-2 gases for our Pt/TiO2 catalysts were ca. 5-10 times of those prepared by a conventional photodeposition method. The molar ratios of H-2 versus O-2 were close to be 2, revealing that the stoichiometric water decomposition occurred. The characterizations of the prepared samples implied that the smaller Pt nanoparticles were highly dispersed on the TiO2 particles by the polygonal barrel-sputtering method. The deposition of the smaller Pt particles increased the Pt surface areas, which can improve the water splitting activities. In addition, the particles deposited by the sputtering method were electron-deficient Pt metals that can enhance the water splitting reaction, whereas those by the photodeposition method were electron-rich Pt metals that reduce the effectiveness of the photocatalytic reaction. These different electron states would play an important role in the remarkable differences in the water splitting activities between the Pt/TiO2 catalysts. Consequently, the polygonal barrel-sputtering method is useful for preparing photocatalysts with the high water splitting activities.