Based on the catalytic property of palladium, GaN nanowires were fabricated by ammoniating Pd:Ga2O3 thin films at 950 ℃, which were deposited onto a Si(111) substrate by radio frequency (RF) magnetron sputtering. Scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM) were used to characterize the structure, morphology, and composition of the samples. Results reveal that the nanowires are single-crystal GaN with a hexa nal wurtzite structure and they have diameters ranging from 20 to 60 nm with lengths of up to several tens of micrometers. Moreover, most of the GaN nanowires have a smooth surface without any impurities and are of high crystal quality. The optical properties of the samples were measured by photoluminescence spectroscopy and three emission bands with peaks at 361.1, 388.6, and 426.3 nm were observed. Additionally, the bandgap UV light emission has a weak blue shift compared to the bulk GaN. We briefly discuss the growth mechanismof the GaN nanowires.