Simulations of the point defect diffusion during the crystal growth process are reported for the investigation of the relationship between the distribution of the oxygen precipitation and point defect concentration in CZ silicon crystals. Distribution of the oxygen precipitation is strongly affected by the point defect concentrations during the growth process. There have been many proposed models for the point defect diffusion during the crystal growth process, and the correspondence between point defect concentrations and grown-in defects has been extensively investigated. In this paper, we have compared the distribution of the oxygen precipitation and the ratio of super-saturation between vacancies and self-interstitials. The experimental results agreed with the results obtained by calculation.