To solve the problem that ZnO ultraviolet photosensors is poor in detecting deep ultraviolet light, a method of fabricating Mg doped ZnO nanowires was proposed to adjust the ZnO energy band, so as to improve the sensitivity of ZnO ultraviolet photosensors in detecting deep ultraviolet light. The MgZnO nanowires were characterized by scanning electron microscope(SEM), energy spectrum analysis(EDS), transmission electron microscope(TEM) and other characterization methods. The results show that MgZnO nanowires were successfully prepared. The ZnO nanowire detector and the Mg doped ZnO nanowire detector were test with the 254 nm deep ultraviolet light, and the test results show that the photoresponse of the Mg doped ZnO detector to the 254 nm deep ultraviolet light was enhanced, the photocurrent increased from 0.02 μA to 0.57 μA. The detector is prepared by Mg doped ZnO nanowires, which can effectively improve the ZnO nanowires detectability in detecting deep ultraviolet light. It will provide beneficial reference for the design and preparation of deep ultraviolet detectors.