摘要Objective: To investigate the effect of Fuzheng Xiaoying Decoction on experimental autoimmune thyroiditis (EAT) model rats and explore its possible mechanism of immune regulation. Methods: Among the 40 female SD rats, 10 were randomly selected as the blank group, and the rest were immunized with pig thyroglobulin and Freund's adjuvant combined with high iodine feeding to make the EAT model. After the model was established, they were randomly divided into three groups: the model group, the selenium yeast tablet group and the Fuzheng Xiaoying Decoction group, which were continuously gavaged for 2 months. The anti thyroid autoantibodies, thyroid function, IL-38 and Th17/Treg distribution were measured. The pathological changes of thyroid tissue were observed by HE staining. Results: Compared with the blank group, the levels of TPOAb and TGAb in the model group were significantly higher(P<0.05). Lymphocyte infiltration was seen in the thyroid tissue of the model group,and also the thyroid follicles were partially destroyed, the shape was irregular, and the colloid distribution was uneven, indicating that the modeling was successful. Compared with the model group, the levels of TPOAb and TGAb in the selenium yeast tablet group and the Fuzheng Xiaoying Decoction group decreased significantly(P<0.05). And the Fuzheng Xiaoying Decoction group had more significant improvement in thyroid follicle destruction and lymphocyte infiltration than the selenium yeast tablet group (P<0.05). Compared with the blank group, the levels of T3, T4, FT3 and FT4 in the model group increased, the level of IL-38 decreased, the proportion of Th17 increased, and the ratio of Th17/Treg increased (P<0.05). Compared with the model group, T4 level decreased, IL-38 level increased in the selenium yeast tablet group and the Fuzheng Xiaoying Decoction group(P<0.05).But there was no statistically significant difference in the reduction of Th17 proportion and Th17/Treg ratio between the above two groups and the model group (P>0.05). There was no significant difference in Treg ratio among the groups. Conclusion: Fuzheng Xiaoying Decoction can significantly reduce the level of anti thyroid autoantibodies in EAT rats by regulating the immunity of EAT rats, and improve the follicular destruction and lymphocyte infiltration of thyroid tissue in rats.