ZnO is a novel direct band-gap semiconductor (Eg=3.3eV at RT) with a high exciton binding energy of about 60meV. The feasibility of using excitionic lasers of ZnO at RT has been demonstrated. There has been an increasing interest in ZnO due to its electrical, optical and piezoelectric properties making suitable for many applications such as light emitting diodes, photodetectors, surface acoustic waves device and so on. SAW filters with working frequency higher than 1GHz will be widely applied in the intending wireless communication, whereas higher resonant frequencies (superior to 2.5GHz) tend to push the limits of conventional photolithography. ZnO/diamond structure as SAW substrates offers an attractive means for relaxation of the lithographic criteria since ZnO has excellent piezoelectricity while diamond has the highest elastic and stiff coefficient and highest sound velocity. ZnO/Freestanding Thick Diamond Films (FTDF) layered structure without additional substrates can avoid restriction of heat dispas sion while making full use of the outstanding characteristics of diamond. The use of smooth nucleation side of FTDF avoids the tedious task of diamond polishing and this simple method would lead to the elaboration of high quality and high power durability SAW devices. In this work, ZnO films are deposited on FTDF by the reactive radio-frequency magnetron sputtering method. The properties of ZnO films are systematically investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe microanalysis (EPMA), photoluminescence (PL) spectra, and Hall measurements. The results are as follows: I Properties of ZnO Films at Various Substrate Temperatures (i) The XRD patterns demonstrate that the crystalline quality of ZnO films tend to increasewith the increase of substrate temperature. (ii) The SEM and measurement shows that with the increase of substrate temperature from 300℃to 600℃, the surface islands of ZnO films tend to become smaller and the surface roughness decreases. With the increase of substrate temperature from 600℃to 750℃, the surface islands of ZnO films tend to become larger and the surface roughness increases. (iii) The PL spectra at the substrate temperature of 750℃demonstrate that high substrate temperature has benefit for the optical properties of ZnO films. The sample at the substrate temperature of 750℃is near the stoichiometry of ZnO characterized by EPMA. (iv) The Hall Effect measurement shows that the samples have high resistivity, which can meet the requirements of SAW devices. II Properties of ZnO Films at Various Radio-frequency Power (i) The XRD patterns demonstrate that the crystalline quality of ZnO films tend to decrease with the increase of partial pressure of Oxygen. (ii) The PL spectra demonstrate that the intensity of PL spectra increases and then decreases, the FWHM decreases and then increases with the peak of 376nm. The results indicate that the ZnO film with an optimal ratio of O_2/Ar≈1 is has the best optical property with low internal defects, which are expected to decrease the insertion and transmission loss for the SAW device. (iii) The Hall Effect measurements show that the samples have high resistivity, which can meet the requirements of SAW devices. III Properties of ZnO Films at Various Radio-frequency Power (i) The XRD patterns, PL spectra and EPMA demonstrate that the sample at the radio-frequency Power of 70W has the best crystalline quality, the strongest PL intensity and the highest Zn/O atomic ratio, which can possibly help improve the understanding of obtaining high quality ZnO deposited on FTDF.。 (ii) The SEM morphology shows that the sample at the radio-frequency Power of 70W is of a relatively clean surface, which is expected to give a high coupling factor for SAW devices. (iii) Hall Effect measurement shows high resistivity of all the samples, which can meet the requirements of SAW devices.