Abstract: Objective To explore the prognosis of patients with Graves disease after iodine ¹³¹I treatment and related risk factors. Methods The clinical history of 1 007 cases of Graves disease admitted in our hospital during 2005-2010 were recorded in detail.All patients were followed up by telephone in 2011,and status of thyroid function was determined in reference with previous diagnosis. Results Total 766 patients completed the last follow-up.After ¹³¹I therapy,102 of the cases (13.4%) had their thyroid function returned to normal,536(69.9%) showed hypothyroidism,and 128(16.7%) remained hyperthyroidism.The statistical analysis showed that the incidence of hypothyroidism was 78.2%,the efficiency of clinical treatment was 90.1% for patients with thyroid weighing less than 30 g;the incidence of hypothyroidism was 74.8%,the efficiency of clinical treatment was 88.1% for thyroid weighting 30-60 g;and the incidence of hypothyroidism was 58.1%,the efficiency of clinical treatment was 72.3% for thyroid weighing more than 60 g(all P＜0.001).The incidence of hypothyroidism was 89.1%,the efficiency of clinical treatment was 97.8% if course of disease was less than 3 months;the incidence of hypothyroidism was 75.4%,the efficiency of clinical treatment was 90.8% if 3-12 months;the incidence of hypothyroidism was 63%,and the efficiency of clinical treatment was 77% if over 12 month(all P＜0.001).Multivariate logistic regression analysis showed that the course of disease less than 1 year,thyroid weighed less than 60 g and secondary isotope therapy was more likely to lead to hypothyroidism.Higher dose of isotope therapy was needed to achieve desired effect if thyroid weighed more than 60 g and course of disease more than 1 year. Conclusion A better efficacy can be achieved if course of disease is less than 1 year and thyroid weighs less than 60 g,but hypothyroidism is also more likely.Higher dose of ¹³¹I is needed if course of disease is more than one year,and the thyroid weighs more than 60 g.