〔Abstract〕 Objective To explore the relationship between methylation of ras-association domain family 1 A(RASSF1 A) gene and iodine nutrition status. Methods 40 SD rats were randomly divided into low iodine group, suitable iodine group, 5-fold high iodine group, 10-fold high iodine group and 20-fold high iodine group. Urine iodine level was determined by ICP-MS method, thyroid hormone level in serum was determined by chemiluminescence immunoassay method, and methylation rate of RASSF1 A gene was determined by BSP method. Results After feeding SD rats with different iodine concentrations for 3 months:(1) the serum FT3 value of rats in each group decreased with the increase of iodine concentration(P<0.05), but FT4 and TSH values had no significant difference among the groups;(2) The methylation rates of CpG island 1 and CpG island 2 in the promoter region of RASSF1 A gene were not significantly different among the groups. Conclusion There is no statistical difference in methylation rate of RASSF1 A gene among groups under iodine induction for 3 months. Iodine may have no effect on methylation of RASSF1 A gene or the body is in compensatory stage.