Abstract: Gallium nitride thin films have been successfully grown on the Ga-diffused Si（111） substrates through nitriding Ga₂O₃ thin films deposited by r.f.magnetron sputtering and the influence of Ga-diffused times on the GaN films were investigated.Fourier Transform Infrared transmission（FTIR） Spectroscopy,X-ray diffraction（XRD）,scanning electron microscopy（SEM） and photoluminescence（PL） are employed to analyze the structure,surface morphology and optical properties of the synthesized samples.The results reveal that the as-grown films are hexagonal GaN.In addition,the results suggest that the crystalline quality and optical properties of the as-formed films were improved with the increasing of Ga-diffused time under the condition of same nitridation temperature and time.But the crystalline quality decreases with the Ga-diffused time increasing to 60min.The optimum Ga-diffused time was 40min.