If residual iodine-131 is found in the neck after iodine-131 treatment, it is necessary to determine the extent of the residue, and to treat the patient in conjunction with whether or not he or she has any residual symptoms, etc. under the judgment of a specialist. Iodine-131 is one of the isotopes of iodine-127 produced in reactors. It can be taken up by cells of thyroid origin. Its natural decay process releases useful rays for the diagnosis and treatment of thyroid cancer and hyperthyroidism. Because the thyroid cells are very capable of iodine uptake, it is unavoidable that there will be more or less residual after taking iodine 131. Iodine 131 residue on the body is mainly the body will appear weakness, no appetite, and even a small number of patients will have nausea, vomiting, dry mouth, the lesion area will be acidic and swollen reaction. There will be no serious reaction. After iodine 131 treatment, patients need to undergo regular checkups, and if there are any abnormalities, they should immediately seek medical advice and adopt appropriate treatment programs under the guidance of the doctor.