Detection of ultraviolet (UV) light is usually based on the photoconductivity effect of semiconductors. Here, we demonstrate the application of a photoelectrochemical cell (PECC) as a self-powered UV-photodetector for detecting the UV light. It is based on the photovoltaic effect of PECCs. By connecting a PECC to an ammeter, the intensity of UV light have been quantiﬁed using the output short-circuit photocurrent (I sc) of the PECC without a power source. This self-powered UV-photodetector exhibits a high photoresponse sensitivity of 269,850%, a rise time of 0.08s and a decay time of 0.03s for J sc signal. The fast time response, high photosensitivity, and good photosensitivity linearity combined with low-cost, environment-friendly, as well as the facile manufacturing process, make this new type of UV-photodetector suitable for practical applications.