To study the relationship between the level of serum thyrotropin receptor antibody (TRAb) and the severity of Crave′s disease. From August, 1996 to June, 1998, 156 outpatients with Crave′s disease were followed up. The level of serum TRAb were measured by radio-receptor-analysis (RRA). Results: ①The level of serum TRAb rose in 90.1% of the untreated group; ②The level of serum TRAb restored to normal after the antithyroid drugs were used and the thyroxine level in serum returned to normal; ③In recurrent patients with the treatment of131I, drugs or operation, the serum TRAb level increased. Conclusion: The level of serum TRAb has great significance in the diagnosis, treatment and follow up of the Crave′s disease.