Abstract: Objective To investigate the protection of different doses of epigallocatechin gallate(EGCG) on ¹³¹I radiation-induced thyroid dysfunction in rat antioxidant system. Methods A total of 52 3-month-old SD rats were randomly divided into six groups, namely, control, model, Euthyrox, EGCG low-dose(25 mg·kg^-1·d^-1), EGCG medium-dose(50 mg·kg^-1·d^-1), and EGCG high-dose(100 mg·kg^-1·d^-1) groups. Except for the control group, ¹³¹I was intragastrically administered for 2 weeks to the five remaining groups to obtain hypothyroid rats. After the hypothyroid rat model was successfully established, the control and model groups received normal saline, whereas the other groups were treated with appropriate medication. After 4 weeks, the levels of serum-free triiodothyronine three(FT₃), free thyroxine(FT₄), and TSH were detected using a biochemical method. The levels of superoxide dismutase, glutathione peroxidase, and peroxidase were also determined. Results The Euthyrox and EGCG groups exhibited significantly elevated serum FT₃ and FT₄ levels compared with the model group. The TSH levels of the Euthyrox and EGCG high-dose groups were significantly reduced. No statistical significance was found in the EGCG low- and middle-dose groups. The superoxide dismutase activity of the Euthyrox and EGCG groups were significantly lower compared with that of the model group, whereas the glutathione peroxidase activity was significantly higher. The catalase levels were also significantly elevated in EGCG medium- and high-dose groups. Conclusion EGCG reduced the effect of radiation on the ¹³¹I oxidative thyroid tissue damage and protected the rat antioxidant system.