In this paper, we investigate the effect of post-implant annealing on the optical and electrical properties of Si-implanted GaN films. Results from several measurement techniques including room temperature photoluminescence (PL), micro-Raman scattering, high resolution X-ray diffraction (HRXRD) and Hall measurement are correlated to study the behavior of damage removal, dopant activation, crystalline quality and residual stress, etc. The Hall measurement demonstrates that reasonable activation percentage is achieved though there is only partial recovery of the PL intensity. Raman scattering shows the decrease of stress within the implanted films after thermal annealing. The carrier concentration increases monotonically with increasing annealing temperature up to 1100°C, which is in agreement with linewidth broadening of near band edge in PL spectrum. Moreover, systematic measurements implies that the implantation induced defects, especially point defects, which could play significant role in either the optical or electrical properties of films, cannot be completely annealed out at 1100°C.