Objective To observe the effect of high iodine on rat'smedicine-induced goiter. Methods Wistar rats were used for the model of rat's medicine-induced goiter and fed different concentration iodine of food for seven months,then extracted thyroid,did the HE staining and AgNOR staining,determined the height of thyroid follicular epithelial cell and area of follicle by mapping analysis system. Results all the experimental groups of rat had got colloid goiter and the higher concentration of iodine in food,as the lower of height of thyroid cell and the gigger of area of follicle.AgNOR counting of abnormal hyperplasia area in all the experimental groups was increasing. Conclusions High iodine made the medicine-induced goiter of rats changed into high iodine's goiter and made some area proliferation actively,maybe change into the carcinomas.