In this study, a nanoflower structured WO3 thin film has been prepared on an etched titanium substrate using a WO3 seeds-assisted hydrothermal reaction method. The WO3 nanoflower-like structure appeared when the growth time arrived at 4.75 h. Subsequently, this film went into a rapid growth stage. The nanoflower (NF) structured WO3 thin film with 8 h of hydrothermal reaction possessed the best photoelectrochemical performance. The photoinduced current density was 2.0 mA.cm(-2) at a bias potential of 1.23 V (vs. Ag/AgCl) under the illumination by a simulated sunlight (100 mW/cm(2)) with a filter air mass (AM) 1.5 G. The improvement of the photoelectrochemical performance of the nanoflower structured WO3 can be attributed to three aspects. Firstly, the light absorption capacity could be increased by the nanoflower structure. Secondly, the reactive sites could be enhanced due to the increased specific surface area of the nanoflower structured WO3. Finally, a direct transfer channel for the photogenerated electrons could be formed by the definite 2-dimentional WO3 nanoflakes linked with the Ti substrate.