Radiotherapy is an important treatment for abdominal and pelvic tumors， but it has a high incidence of the adverse reaction radiation enteritis. Abdominal and pelvic radiotherapy can induce apoptosis of intestinal crypt cells， destroy the intestinal barrier and change the composition of gut microbiota. Dysbiosis of gut microbiota can aggravate radiation enteritis. Fecal flora transplantation， as well as the use of probiotics， prebiotics and antibiotics can regulate gut microbiota， which is an effective method to prevent and treat radiation enteritis.