Diarrhea is one of the common clinical manifestations of hyperthyroidism, with an incidence of 25% to 36%. It is due to the abnormal vagal nerve function caused by elevated thyroxine, resulting in accelerated gastrointestinal motility, accelerated intestinal emptying and decreased absorption, which leads to symptoms such as increased stool frequency, mushy stools or diarrhea. Sometimes patients may excrete undigested food or develop steatorrhea without abdominal pain, mucus, or pus and blood. Stool examination is mostly normal, and there is no growth of pathogenic bacteria. Hyperthyroid diarrhea can be easily misdiagnosed as chronic colitis, irritable bowel syndrome and functional dyspepsia, etc. A good differential diagnosis is needed. Generally speaking, hyperthyroid diarrhea has the following characteristics for differentiation: ① Recurrent diarrhea without obvious abdominal pain, relatively stubborn, often accompanied by clinical manifestations such as weakness, emaciation, panic and irritability. ②Intestinal examination without obvious abdominal pressure, only hyperactive bowel sounds, no organic lesions on X-ray barium meal fluoroscopy and colonoscopy. ③Antibiotic treatment is ineffective and sensitive to antidiarrheal drugs. ④Serum thyroxine level is significantly elevated. Once the diagnosis of hyperthyroid diarrhea is clear, the first thing is to treat the hyperthyroidism and standardize the treatment with anti-thyroid drugs to normalize the level of thyroid hormone in order to reduce the impact on the gastrointestinal tract and effectively relieve the diarrhea symptoms. Secondly, we can consider the application of traditional Chinese medicine to control diarrhea, such as Chinese medicine to strengthen the spleen and permeate dampness, clear heat and dry dampness, and astringent intestines to stop diarrhea, such as ginseng lingbaijusan plus or minus, plus flavor zhu che tang. Some anti-diarrheal western medicines have obvious therapeutic effects, but they have too many side effects and should not be used frequently. Diet should be light, easy to digest, low-fat and less residue food, small amount of meals, chew slowly, avoid high-fat and spicy stimulating food, and eat less iodine-containing food such as seaweed, nori and sea fish.