Abstract: We report a case of ¹³¹I therapy in a patient with congenital absence of single thyroid gland lobe combined with Graves' disease and recurrence after methimazole therapy. We analyzed the characteristics of this case on the basis of clinical symptoms; auxiliary examination, including serological tests, thyroid ultrasound, and SPECT/CT fusion imaging of neck and chest. Understanding about the congenital absence of single thyroid gland lobe combined with Graves' disease was deepened through literature review. ¹³¹I therapy must be employed as early as possible when a patient with congenital absence of single thyroid gland lobe combined with Graves' disease exhibits recurrence after regular oral antithyroid drug therapy. ¹³¹I therapy is still an ideal method for patients with congenital absence of single thyroid gland lobe combined with Graves' disease and recurrence after methimazole therapy.