6H-SiC single crystal specimens were implanted at 600 K with 100 KeV He ions to three successively increasing fluences and subsequently annealed at different temperatures ranging from 600℃ to 1200℃ in vacuum. After the annealing, the samples were investigated by using Raman scattering spectroscopy and photoluminescence spectrometry，respectively. Both of the two methods showed that the damage induced by helium-ion-implantation in the lattice is closely related to the dose. The thermal annealing brings about recovery of the damage，and different levels of damage require different annealing temperature to recover efficiently. It is indicated that different annealing stages involve different mechanisms，corresponding to recombination of point defects，formation of He-vacancy complexes，and nucleation and coarsening of bubbles，respectively. The experimental results indicate that high temperature implantation is an effective way to avoid amorphization of the implanted layer due to damage accumulation. Helium implantation can be used to introduce buried nanoscale cavities as the nucleation site for the buried oxide in a well defined region proposed for an alternative and more economical method of manufacturing SiC-on-Insulator （SiCOI）.