Objective:To investigate the effect of indigo on Hashimoto’s thyroiditis and possible mechanism through comparison of the changes of thyroid globulin antibody (TGAb), thyroid peroxidase antibody (TPOAb), interleukin-10 (IL-10) and interferon-γ(IFN-γ) in experimental autoimmune thyroiditis rats before and after treatment. Methods After adaptive feeding for 1 week,30 SD female rats were randomly divided into the normal control group(10 rats)and modeling group(20 rats). The modeling group was treated with iodine at high concentration, and the normal control group was given distilled water. From 4th week,the modeling group was treated with porcine thyroglobulin (pTG) of complete Freund’s adjuvant (CFA) and the successful modeling rats were randomly divided into the model control group (10 rats) and treatment group of traditional Chinese medicine (10 rats). The treatment group were treated with indigo decoction,with a course of 42 days. The levels of serum TGAb、TPOAb、INF-γ and IL-10 in all groups were tested by ELISA. And the pathological sections of thyroid gland tissue were observed by light microscopy.  Results:After treatment, the serum levels of TPOAb and TGAb in the treatment group were decreased compared with the model control group (P<0.01). Compared with the normal control group, the serum IL-10 levels of all modeling groups were decreased (P<0.01), and the levels of IL-10 in the traditional Chinese medicine treatment group were increased compared with the model control group after treatment (P<0.01). Compared with the normal control group, the level of IFN-γ in the model control group and the traditional Chinese medicine treatment group were significantly increased (P<0.01); compared with the model control group, the IFN-γ level of traditional Chinese medicine treatment group was decreased (P<0.01).  Conclusion:Indigo regulated the level of TGAb, TPOAb, IL-10 and IFN-γ in model rats,which improved Hashimoto’s thyroiditis.