Abstract: Ga₂O₃ thin films were deposited on ZnO/Si（111） substrates by sputtering Ga₂O₃ target in a JCK-500A radio frequency magnetron sputtering system.Then GaN nanostructured thin films comprised of regular hexagonal crystal grains have been successfully synthesized by ammoniating Ga₂O₃ films at the temperature of 850℃ for 15 min in a quartz tube.X-ray diffraction（XRD） reveals that the synthesized GaN is of a hexagonal wurtzite structure with lattice constants a=0.318 nm and c=0.518 nm.X-ray photoelectron spectroscopy（XPS） confirms the formation of bonding between Ga and N,and yields the surface stoichiometry of Ga:N of 1:1.Scanning electron microscope（SEM） and atom force microscope（AFM） are taken to examine the morphology of GaN,indicating that the as-grown GaN films are smooth and uniform.Transmission electron microscope（TEM） demonstrates the films are composed of the regular hexagon grains and selected-area electron diffraction（SAED） further shows that the GaN is a hexagonal wurtzite structure.Finally,the growth mechanism is also briefly discussed.