A practical computer simulation technique has been developed to predict oxygen precipitation behavior in Czochralski silicon wafers during various thermal processes. In this simulation, an empirical factor is introduced in the initial and boundary conditions of the Fokker-Planck equation of the oxygen precipitation in order to make up an incomplete assumption of a homogeneous nucleation process proposed bg Schrems et al.(1) The empirical factor is constructed as a function of heat-treatment temperature and interstitial oxygen concentration so as to describe characteristic phenomena of the precipitation nucleation processes in the 450 to 800 degrees C range. Futhermore, an experimentally measured thermal history during a crystal growth process, which strongly influence the oxygen precipitation behavior in the subsequent thermal process, has been taken into consideration. The calculated results agree fairly well with the experimental results for a variety of thermal processes. This semi-empirical simulation technique thus provides an advantageous tool for industrial optimization of the oxygen precipitation characteristics.