The treatment of iodine 131 after total thyroidectomy is to use the γ-ray and β-ray released by iodine 131 to kill the residual tissues or hidden foci of thyroid cancer after total thyroidectomy, which can effectively reduce the risk of recurrence and death. The residual lesion tissue will concentrate iodine 131 after oral administration of iodine 131, which releases γ-rays and β-rays, which are highly effective in killing the lesions. The significance of radioactive iodine therapy is that iodine 131 can remove hard-to-detect foci in the residual thyroid tissues after surgery in order to reduce the recurrence and metastasis rates. Gingival pain, nausea, vomiting, skin rash, etc. may occur with the use of iodine 131, and consult the doctor promptly when discomfort occurs. Iodine 131 treatment is contraindicated in pregnant or breastfeeding women, as well as in patients who have concomitant acute myocardial infarction or acute hepatitis. If patients need to be treated with iodine 131 after total resection of thyroid cancer, it is recommended to be carried out under the guidance of a doctor, and do not take treatment by yourself, so as to avoid delaying the condition and triggering adverse consequences.