In order to achieve ultraviolet detection without power supply， a self-powered ultraviolet detector based on WO₃ nanosheets is constructed. The uniform WO₃ nanosheets have been successfully synthesized on fluorine-doped tin oxide substrate via a facile hydrothermal method. Then， the morphology， composition， and structure of the samples are systematically characterized， which indicates that WO₃ nanosheets are monoclinic with an average length of 2 μm and a mean thickness of 200 nm. Furthermore， the ultraviolet detector based on WO₃ nanosheets has been fabricated and measured without bias voltage for its photodetection performances， which reveals high values of photocurrent about 171 μA， rapid response with rise time around 25.7 ms and decay time around 38.7 ms， outstanding stability and self-powered property under the cycled irradiation of 365 nm ultraviolet light.