Using on-line measurement of plasma emission spectra during reactive magnetron sputtering, the growth of ZnO films was studied with the variation of O2 flow and deposition temperature, ranging from room temperature to 750℃. With the structural characterization and measurement of optical properties, we revealed the role of growth temperature and O2 flow in the growth of ZnO film. The results showed that O2 flow was important in determining the sputtering yield of Zn target. When the flow ratio of O2 to Ar+O2 (R)>0.75%, the sputtering yield of Zn decreased linearly with increasing O2 flow. When R was in the 10%—50% range, the concentration of oxygen varied slowly, which may be useful for the control of film growth. The intensity of emission spectrum of atomic Zn at 481.3 nm varied with increasing deposition temperature T. When T550℃, the intensity increased sharply with increasing deposition temperature. By controlling the deposition temperature, a high-quality film with the composition close to stoichiometric ZnO was fabricated on Si(001) substrate at 750℃ and ultraviolet photoluminescence was detected at room temperature.