An oscillator based on a ZnO/Si layered surface acoustic wave (SAW) device was fabricated for the application of UV detection. An oscillator circuit composed of a high frequency amplifier, a match network and a layered SAW device was constructed, in which ZnO thin film is simultaneously used as an active layer for UV detection and a piezoelectric layer for exciting a high-ordered surface acoustic wave. The microstructure and crystallization of the ZnO films were investigated using the scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The SAW oscillator shows an excellent performance with the resonance frequency of 751 MHz and phase noise of -94.7 dBc@100 kHz. The UV light illuminations were varied with vertical and horizontal positions to analyze the influence on the frequency responses. An extreme frequency shift of 710 kHz under UV intensity of 30 μW/cm2 was obtained at the center of the IDT electrodes.