One-dimensional ZnO nanostructure is especially attractive because of its unique properties such as high surface-to-volume ratio and a large exciton binding energy, but how to put it into a device is still a challenge. In this article, we show that a novel lateral metal-semiconductor-metal ultraviolet detector composed of ZnO nanowires is fabricated on glass substrate by a single-step hydrothermal approach. The fabricated photodetector demonstrates that the response to UV illumination in air is fast, the rise time is about 4 s, and the fall time is about 5 s, which could be attributed to the fact that the adsorption and the desorption of water molecules in the air onto oxygen vacancy of the nanowire significantly influence the photoresponse.