Abstract： Objective:To evaluate the characteristics of changes in thyroglobulin antibody (TgAb), thyroid stimulating hormone receptor antibody (TRAb), thyroid peroxidase antibody (TPOAb) and thyroid stimulating antibody (TSAb) and the value of the combined semi-quantitative score in assessing the effectiveness of 131I treatment for Graves' hyperthyroidism (GH). Methods:Retrospective analysis of clinical data of 512 patients with GH who underwent 131I treatment at Shanghai Ruijin Hospital, School of Medicine, Shanghai JiaoTong University from January 2000 to August 2021. The patients comprised 101 males and 411 females, aged (38±12) years. According to the efficacy evaluation, patients treated with 131I were divided into four groups: hypothyroidism group, complete remission group, partial remission group, and ineffective group. The first three groups were the effective group (Group A) with a total of 431 cases, and the ineffective group (Group B) had 81 cases. According to the time after 131I treatment, Group A was further divided into 4 groups: Group A1 (within 1 year after 131I treatment; 80 cases); Group A2 (1-4 years after 131I treatment; 193 cases), Group A3 (5-9 years after 131I treatment; 90 cases); Group A4 (more than 10 years after 131I treatment; 68 cases). The GH patients enrolled in the study underwent continuous and combined measurements of free triiodothyronine, free thyroxine, thyroid stimulating hormone, TgAb, TRAb, TPOAb, and TSAb levels were performed at 4 weeks, 7 weeks, 3 months, 6 months, 12 months, or annually after 131I treatment. The semi-quantitative score ranges for single and four combined thyroid antibodies (TgAb, TRAb, TPOAb and TSAb) were 0-3 and 0-12 points, respectively. The intergroup differences were compared using paired t-test. Results:TgAb, TRAb, TPOAb, and TSAb increased to varying degrees after 131I treatment, and the abnormal increase period could last for 29, 21, 26, and 26 months, respectively. Thereafter, they exhibited different degrees of decline (until it could be negative). In group B, A1, A2, A3 and A4, the combined semi-quantitative scores of four thyroid antibodies were 7.43±2.31, 5.41±2.23, 4.43±2.40, 2.15±1.99 and (1.52±1.50) score respectively. The differences between groups A1 and A2, A2 and A3, A3 and A4, A1 and B, were statistically significant ( t=3.237, 8.358, 2.252,-5.639, all P<0.05). After 131I treatment for 5 and more than 10 years, the positive rates were 64.56% (102/158) and 55.88% (38/68) for TPOAb, 34.81% (55/158) and 33.82% (23/68) for TgAb, 18.35% (29/158) and 11.76% (8/68) for TRAb, 24.68% (39/158) and 17.65% (12/68) for TSAb, respectively. Conclusions:The semi-quantitative score of the combination of the four thyroid antibodies could be used to assess the severity of thyroid autoimmune status and its evolution. The initial onset of GH is characterized by a significant increase of TRAb, and the antibody index is relatively stable after 5 years of 131I treatment, and TPOAb positive rate of more than 50% suggests the presence of hypothyroidism resulting from Hashimoto's thyroiditis.