Abstract: The expression of Bax and p53 in rabbits thyroid cell are detected using immunohip-tochmistry after certain dose of 131I uptaken by thyroid one week later. The results show that the expression rate of Bax in 131I group is 88. 9%, and significantly higher than that in control group (P <0. 005); no expression of p53 is found in both 131I group and control group. It indicates that the apoptosis in thyroid cell induced by 131I radiation closely related to the expression of Bax genes.