The effect of nitrogen on the oxygen precipitation during high-temperature annea ling in Czochralski silicon was investigated. After annealing under different co nditions, the variation of oxygen precipitation and the bulk microdefects(BMDs) density with annealing time at high temperatures was measured, and transmission electronic microscope was used to observe the microstructure of oxygen precipita tes. It was found that nitrogen doping strongly enhanced oxygen precipitation du ring high-temperature annealing; furthermore, the densities of BMDs in the annea led NCZ samples were higher than those in the corresponding CZ ones. Therefore, it is considered that the nitrogen can react with vacancy and oxygen to form N-V -O complexes to enhance the nucleation of oxygen precipitates, and the oxygen pr ecipitates are plates with strong inner stress.