Abstract.The electronic and structural properties for RF magnetron sputtering deposited ZnO thin films grown on Si substrate was obtained by using X-ray diffraction (XRD) and reflection electron energy loss spectroscopy (REELS). XRD spectra show the intensity of the diffraction peak increases with increasing the growth temperature with (002) is strongest diffraction peak. The particle sizes for (002) are increase from 10.2 nm to 60.2 nm with increasing growth temperature from room temperature to 500 o C, respectively. The band gap of ZnO thin films REELS spectra are 3.1 0.1 eV. The dominant peak from REELS at about 18 eV is ascribed to a bulk Plasmon excitation, which represents the collective oscillation of the valence electrons excited by the incident fast electrons.