Objective To observe the pathological characteristics of thyroiditis induced by iodine excess and thyroglobulin (Tg) immunization and to explore the mechanism of thyroiditis induced by iodine excess. Methods NOD mice were used for intaking 0.05% Nal water and(or) Tg immunization. Morphologic change in thyroid and apoptosis were observed. The levels of serum TT4, TSH, thyroglobulin antibody (TgAb) and thyroid peroxidase antibody (TPOAb) were measured. Responding to Tg, lymphocytic proliferation of lymph node and spleen, interleukin-4(IL-4)and γ-interferon(IFN-γ) levels in culture medium of splenocytes were detected. Real-time PCR Was used to detect mRNA expressions of IL-4, IFN-γ, chemokine ligand 10 (CXCL10) and intercellular adhesion molecular-1(ICAM-1) in thyroid. Results Distended thyroid follicles,colloid accumulation, intense lymphocytic infiltration and disorganization were seen in thyroid of iodine excess group, along with increased apoptosis of thyroid cells(34.66～ 2.78 vs 5.11±0.62 ,P<0.01). The levels of TT4 were lowered while TSH raised ,but no production of thyroid-specific autoantibodies was revealed. Lymph node and spleen cells showed positive respornse under stimulation of Tg. The level of IFN-γ[(1. 272±0.049 vs 1. 139±0. 025)ng/L,P<0. 01] was raised in culture medium of splenocytes but not IL-4. The expression of IFN-γ, CXCLI0 and ICAM-1 mRNA were increased in thyroid. But in Tg group, some lymphocytes were scattered in thyroid, autoantibodies emerged ,and the level of IL-4 was increased in cuhure medium of splenocytes[(18. 508±0. 113 vs 13. 368±0. 016)ng/L, P<0. 01]. ledine excess combined with Tg enhanced these inflammatory reaction. Conclusion Iodine excess induced thyroiditis in NOD mice. The process seems to be Th1 response dominant organ-specific autoimmune diseases. Iodine excess and Tg immunizatiou play a synergistic role in inducing experimental autoimmune thyroiditis.