Self-supporting ZnO nano-networks have been demonstrated by a substrate-free chemical vapor deposition process for the application as flexible ultraviolet (UV) photodetector. The device shows a responsivity of ∼300 mA W-1over a wide wavelength range from 254 to 365 nm and a high UV/visible rejection ratio of more than 104. More interestingly, a short 90%-10% decay time of <0.12 s can be observed in the air atmosphere, and the current can fully recover to its original dark value within 1 s after switching off the light. The quick response speed should be associated with the wire-wire junction barriers and the adsorption/desorption process of oxygen molecules on the oxygen vacancies near the surface of the ZnO. In addition, the photocurrent, the dark current and the response speed of the ZnO nano-networks flexible UV photodetector nearly stay the same under different bending conditions, suggesting the excellent photoelectric stability and repeatability. Such a simple and cheap way for fabricating self-supporting ZnO-based devices has broad application prospects in the fields of flexible and wearable electronic devices.