Flow pattern defects(FPDs) in as-grown and rapid thermal annealed heavily Sb-dop ed silicon wafers was investigated. The experimental results show that the dens ity of FPDs can be reduced after high temperature annealing, and H2 is the most effective annealing atmosphere. The mechanism of elimination of FPDs is also discussed from the relationship between heavily doping Sb and interstit ial oxygen concentration. The heavily doping Sb influences not only the distribu tion of initial oxygen concentration in CZSi wafer, but also the formation and h eat behavior of grown-in void defects.