Abstract: Objective Find out the direct influencing factors for the treatment of the Graves’disease by 131I. Method 302 patients with Graves disease were treated with 131I.An Iodine absorption test had been done before the treatment. Before and three years after the treatment,patients' different serum factors such as T3, T4, FT3, FT4, s-TSH, TRAb and TPOAb were detected. According to their thyroid functions 3 years after treatment,patients were divided into 3 groups as follows: relapse group, cured group and hypothyroidism group. Age, gender, therapeutic dose, Iodine absorption efficiency, T3, T4, FT3, FT4, s-TSH, TRAb and TPOAb were compared among the 3 groups.Results For factors as gender, Iodine absorption efficiency, blood serums T3, T4, FT3, FT4 and s-TSH, there were no statistical differences among the 3 groups(P > 0.05).Age of hypothyroidism group was lower than that of relapse group（P<0.05）. 131I therapeutic dose of relapse group was higher than that of cured group （P<0.05）.TRAb of cured group was higher than that of hypothyroidism group (P < 0.05).For serum TPOAb before treatment,hypothyroidism group was the highest,relapse group was the lowest,while cured group was in between, there were statistical differences (P < 0.01) among the 3 groups. Conclusion Age, 131I therapeutic dose, blood serum TRAb and TPOAb had something to do with the prognosis of Graves' disease treated by 131I. Hypothyroidism was inclined to younger patients.A few serious patients could not be cured or relapsed easily even though a much higher therapeutic dose was used.Patients with lower TRAb and higher TPOAb before treatment were also prone to hypothyroidism.