Hexagonal wurtzite GaN materials with nano-structure have been fabricated on Si (111) substrates via ammoniating ZnO/Ga2O3 films at different temperatures. ZnO layers and Ga2O3 films were deposited in turn on Si (111) substrates by radio frequency (r.f.) magnetron sputtering before the ammoniating process. The structure and composition of GaN crystal were studied by X-ray diffraction(XRD) and fourier transform infrared spectrophotometer(FTIR).The morphology of the samples was studied by scanning electron microscopy (SEM).Through the analyses of the measurement results , a conclusion can be drawn that hexagonal wurtzite GaN with nano structure was grown on Si (111) substrates with the assistance of the volatilization of ZnO, and the ammoniating temperature has a great effect on the fabrication of GaN nano materials with this method.