Objective：To study the effect of the different development periods to the homeodomain transcription factors Nkx2．2 and Nkx6．1 expression in rat pancreas．Methods：Pancreas were isolated from SD rats on gestational days 1 8．5．new h()rn and adult by microscope．Pancreas were probed by the pancreatic molecule marker—insulin and amylase．A semi—quantitative reverse transeriptase polymerase chain reaction (RT-PCR)was performed to assess the expression of transcription factors Nkx2．2 and Nkx6．1 in diferent developing periods in rat pancreas．Results：Nkx2．2 and Nkx6．1 gene expression increased from gestation to new born and then decreased in adult．Conclusion：Different development periods can regulate the expression of Nkx2． 2 and Nkx6．1 gene．New born period is a special time when loss nutrition from mother body，and initial of autoimmune and digestion system． Fhe resire in cell neogenesis may lead to the increase in the gene expression of the homeodomain transcription factors Nkx2 2 and Nkx6． 1．