A series of Pt–TiO2 photocatalysts were prepared by a facile precipitation–photoreduction method under different pH conditions, using H2PtCl6 as platinum precursor. The microstructure and chemical state of Pt loaded on the surface of TiO2 were analyzed by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). It was revealed that the size and distribution of Pt nanoparticles on TiO2 surface is closely related to the initial pH of H2PtCl6 solution. The optimal pH value for forming highly dispersed Pt nanoparticles is 12. The photocatalytic activities of the prepared samples were investigated in terms of hydrogen production. The results indicated that the Pt–TiO2 sample prepared by precipitation–photodeposition method shows much higher activity than that prepared by traditional photodeposition method.