SnO2 nanorod arrays are prepared by hydrothermal synthesis in autoclave at glass substrate. The structures and morphologies of SnO2 samples are investigated by X-ray diffraction(XRD) and scanning electron microscopy(SEM). The growth principle of SnO2 nanorod arrays is explained. Ethanol sensing properties of SnO2 at different reactive times in autoclave and different annealed temperatures are studied. The best test parameter is found,and ultraviolet (UV) light enhanced ethanol sensing properties of SnO2 are investigated at room temperature. The results show that SnO2 nanorod arrays prepared in autoclave 6 h and annealed at 500 °C exhibit the best gas sensing property at room temperature. The gas sensitivity and stability of the SnO2 are increased by 365 nm UV light. And response and recovery time are shorten to 5 s.