In this study, the reactive rf magnetron sputtering was used to deposit zinc oxide (ZnO) thin films on SiO2/Si substrate at room temperature. The thermal treatment procedure was carried out to improve the luminescence characteristics of ZnO thin films. The physical characteristics of ZnO thin films with different post annealing process were obtained by the analyses of XRD and SEM. The electron spectroscopy for chemical analysis (ESCA) was used to analyze the chemical states of ZnO thin films. In optical properties, the photoluminescence spectrometer was used to measure the photoluminescence characteristics (PL). According to the results of experiments, the chemical states of ZnO thin films were changed after different post annealing. The photoluminescence characteristics were obtained at different wavelength, and the results indicated that they were affected by the chemical states of ZnO thin films. With 900¢J annealing, the strongest green emission and UV emission intensity can be obtained under the air ambient and the oxygen ambient, respectively. The reason was due to the variation of the proportion of oxygen vacancies and O-Zn bond within the ZnO thin films.