Ultraviolet (UV) sensor based on nanostructured ZnO/Si Surface Acoustic Wave (SAW) devices is studied in this paper. The ZnO films sputtered onto Si (100) substrate showed a preferred (0002) orientation and good photoluminescence emission. For the SAW device with a wavelength of 64 um, a frequency downshift of ~ 1.4 kHz was observed at the Rayleigh mode under a UV light intensity of 0.6 mW/cm2, whereas the frequency downshift for the Rayleigh mode was increased to 8.3 kHz after integrating ZnO nanorods (NRs) in the ZnO/Si SAW devices. For the SAW device with a wavelength of 20um irradiated under a UV light intensity of 0.6 mW/cm2, a frequency downshift of 25 kHz for the Sezawa mode was obtained compared to a shift of 12 kHz for the Rayleigh mode. After depositing ZnO NRs, the resonant frequency for the Rayleigh mode was increased to 27.4 kHz under the same UV intensity illumination, due to the significant increase in surface-to-volume ratio.