Well-crystallized nanopolycrystalline thin films of cubic strontium titanate, SrTiO3, have been prepared on the TiNi-deposited Ni substrate in Sr(OH)2 aqueous solutions at temperatures between 130 and 200°C under saturated vapor pressures. The microstructure and morphology of the films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The photoelectrochemical properties of SrTiO3 thin films on TiNi-deposited Ni substrate were investigated on a three-electrode assembly. The grain sizes increased from 30 nm to 300 nm and the relative crystal intensity in XRD pattern increased with the reaction temperature. Its photocurrent increasesdfirst with the grain size, then decreased. When the grain size of the film is about 200 nm, the photocurrent is highest.