The common adverse reactions of patients after iodine 131 treatment include radiation thyroiditis, gastrointestinal adverse reactions, hematologic adverse reactions, salivary gland damage, abnormal taste, oral mucositis, lacrimal gland damage, radiation pneumonitis and pulmonary fibrosis. The main symptom of radiation thyroiditis is neck pain and swelling, which is mostly mild, transient, and gradually decreases. Patients with a large number of residual glands often experience painful and uncomfortable swallowing, and a very small number of patients may experience severe or persistent pain and edema of the larynx. Gastrointestinal adverse reactions are caused by hypothyroidism after iodine 131 treatment, which causes a decrease in basal metabolic rate and a slowing of gastrointestinal motility. Hematologic adverse reactions are dominated by a decrease in white blood cells, mostly mild. The main symptoms of lacrimal gland injury are tear spillage, photophobia and ocular dryness, which are often mild and mostly resolved on their own. It is recommended that patients after treatment with iodine 131 follow the doctor’s instructions to check thyroid hormone levels in a timely manner and take appropriate care measures.