The diet of rectal cancer patients during radiotherapy needs to pay attention to certain matters: 1. diet that can be easily digested and absorbed; rectal cancer patients mostly have recurrent and prolonged diarrhea, poor digestion and absorption, so the diet should pay attention to more food that can be easily digested and absorbed. 2. food with high nutritional value; tumor patients consume more and their nutritional status gradually deteriorates, so they can consume fish soup, eggs, protein powder and other high nutritional food. 3, diet rich in water, patients have more bowel movements or long-term low fever, sweating and water deficiency. The side effect during radiotherapy is radioactive enteritis, which is mainly manifested as increased number of stools, watery stools and water deficiency, so it is necessary to drink more water or soup. 4. light diet, rectal cancer patients mostly have blood in stool, so they should eat less or no irritating and spicy food, in order to relieve symptoms such as loss of appetite, nausea and even vomiting caused by radiotherapy, it is appropriate to eat light diet, avoid smoking, deep-frying and other greasy food. 5. Appropriate consumption of fiber-containing diet, dietary fiber has strong water absorption, which can increase the volume of feces and make feces form. 6. 1-2 kinds of probiotics starting one week before radiotherapy can adjust the intestinal flora and significantly reduce the probability of diarrhea caused by radiotherapy.