ZnO thin films with a strong c-axis orientation have been successfully deposited on quartz glass substrates at room temperature by radio frequency (rf) magnetron sputtering technology. X-ray diffraction, Rutherford backscattering, and prism coupling method were used to investigate the structure and optical properties of ZnO thin films. X-ray diffraction results shown lower sputtering pressure is propitious to increasing the crystallinity, and enhancing the c-axis orientation of the films. Rutherford backscattering analysis revealed that the films were stoichiometric ZnO, and as the sputtering pressure decreasing, the deposition rate were increased from 0.758 3nm/min to 2.892 nm min for sputtering pressure in the range from 1.0Pa to 0.5Pa. Under the lower sputtering pressure (0.5Pa) condition, the results obtained by prism coupling method investigation confirmed that the effective refractive index of ZnO films (no=1.8456，ne=1.8276) at a wavelength of 633nm is more close to Crystal Refractive index.