目的　探索快速诊断唐氏综合征的方法。方法　应用 2 1号染色体特异的寡核苷酸引物对 12份外周血淋巴细胞培养标本进行了引物原位标记反应。结果　 4例唐氏综合征患儿标本中 ,中期分裂相 2 1号染色体标记率平均为 99% ,平均 93%的间期细胞核显示 3个标记信号。 8例习惯性流产夫妇的标本中 ,中期分裂相 2 1号染色体标记率平均为 98% ,平均 91%的间期细胞核显示 2个信号。荧光信号清晰明亮 ,整个反应在 4～ 5小时内完成。结论　应用引物原位标记技术可快速准确检测 2 1号染色体数目异常 ,诊断唐氏综合征。 Objective To explore the method of rapid diagnosis of Down Syndrome. Methods Twelve peripheral blood lymphocyte culture samples were labeled by in situ labeling with chromosome 21-specific oligonucleotide primers. Results Among the 4 children with Down’s syndrome, the mean chromosome number of chromosome 2 1 was 99%, with an average of 93% of the interphase nuclei showing 3 marker signals. In 8 cases of habitual abortion couples, the average number of chromosomes on chromosome 2 1 was 98%, with an average of 91% of the interphase nuclei showing 2 signals. Fluorescent signal clear and bright, the entire reaction in 4 to 5 hours to complete. Conclusion Primer in situ labeling technique can be used to rapidly and accurately detect chromosome 21 abnormality and diagnose Down Syndrome.