Abstract: Human genome project has made a great progress, but the study about the gene expression regulation is still at the beginning. It's found that many diseases such as cancer are related to the deactivation of some gene expressions, whose epigenetic mechanisms involve DNA methylation, histone acetylation and other structural changes in chromatin. That disturbs the normal gene expression regulation and cell multiplication, which finally induce the carcinogenesis. So the re-expression of inactive genes may play a part in inhibiting the carcinogenesis. On the basis of the view, histone deaeetylase (HDAC) inhibitor has a variety of applications in the study of disease and tumor, including the thyroid carcinoma. Furthermore, it comtribute to the mew way of the redifferentication and radioidine therapy against poorly differentiated thyroid carcinoma.