Oxygen gettering in Si by the He induced cavity layer was investigated in this work. A cavity layer was generated in Si sample by He implantation and annealing. The morphology of the cavity layer depending on the dose of He and the annealing temperature was presented in the paper. This cavity layer may serve as an efficient oxygen gettering layer during the high temperature oxidation process and accumulate the oxygen from the annealing atmosphere as well as the implanted oxygen. The phenomenon gives the idea that the cavity layer can be employed to define the oxide formation in Si and further to facilitate the formation of the buried oxide layer (BOX) in Si aiming at the Si-on-Insulator (SOI) structure fabrication. The oxygen gettering ability of the cavity layer in Si was investigated by cross section transmission electron microscopy and auger electron spectroscopy.