The GaN films grown on sapphire by metal-organic chemical vapor deposition (MOCVD) have excellent crystalline quality (χmin=2.00%). Combining Rutherford backscattering/channeling (RBS/C) and high-resolution X-ray diffraction (HXRD) measurements, we investigate the radiation damage in GaN films with various doses and angles of Mg+-implantation. The results of experiments reveal that the radiation damage rises with the increasing implantation dose. Under the dose of 1×1015atom/cm2, χmin is less than 4.78%, and when implantation dose exceeds the threshold of 1×1016atom/cm2, χmin will be up to 29.5%. Random implantation causes more serious damage than channeled implantation, and in a definite range the damage level rises with a larger implantation angle. At the implantation angles of 0°,4°,6°and 9°deviating from〈0001〉, χmin(%)is 6.28,8.46,10.06 and 10.85, respectively, at a dose of 4×1015atom/cm2. After annealing at 700℃ for 10min and then 1050℃ for 20s, the damage recovers to some extend. The crystalline quality of the sample with 1×1016atom/cm2 implanted was reduced to 19.08%. In addition, the annealing condition of 1000℃ for 30s is more efficient and the damage recovers better.