Diarrhea after radiation therapy is very strong, should pay attention to supplemental nutrition, ensure drinking water, drug treatment. After radiation therapy, tumor patients may have symptoms such as loss of appetite, vomiting, local skin pain, redness and swelling, etc. Rectal radiotherapy causes radiation proctitis, and diarrhea may also occur as a side effect, patients should strengthen nutrition, eat less and more frequent meals, and avoid spicy and stimulating food intake. If the symptoms of diarrhea are more serious, patients should pay attention to increase water intake to avoid dehydration caused by diarrhea. When diarrhea occurs more than 5 times a day, anti-diarrhea medication such as montelukast should be taken under the guidance of a doctor for treatment. If the situation persists for a longer period of time, it is also necessary to pay attention to the primary intestinal tumor itself causing diarrhea, and timely treatment should be carried out. It is recommended that the patient should consult the doctor in time, and then take active treatment after clarifying the cause of the disease, so as to avoid delaying the condition.