SIMOX SOI structures were formed by oxygen ion implantation with a dose of 2 1018 ions/cm2 at 180kev and post-implantation annealing at $1250^{circ}C$ for 6 hours in nitrogen ambient. The oxygen redistribution process during post-implantation annealing was examined by AES and TEM. The electrical property of the structure was investigated by SRP method. We could find oxygen precipitates in SOI layer was discussed. And the limiting factor to the decrease of the precipitates during post-implantation annealing was discussed also.