The incidence of radiation enteritis in pelvic tumor radiation therapy is reported in the literature to be as high as 59.5%, and there are no measures to prevent the occurrence of radiation enteritis in western medicine. Many patients delay or terminate the radiotherapy program, which not only affects the quality of life of patients, but also may affect the overall treatment effect of tumor. In Chinese medicine, this disease belongs to the category of “diarrhea” and “abdominal pain”. It is believed that the pathogenesis of this disease is a combination of deficiency of the tumor’s vital energy and the reality of the accumulation of cancer toxins, coupled with the invasion of external radiation, so that the spleen qi is deficient, water-dampness is not transformed, phlegm and stasis are intertwined and the intestinal ligaments are burned and the damp-heat toxins accumulate, blood stasis and phlegm coagulation, damp-heat injection, rotten flesh and blood, and the depletion of fluid and qi due to diarrhea. Symptoms include weakness, increased frequency of stools, loose stools, lack of transformation of finished grains, anal drop, dry mouth without drinking, and other manifestations of positive deficiency, or with downward injection of red and white mucus, burning anal stool with fresh blood, and other manifestations of evil with internal concentration of damp-heat and toxic evil. Since radiotherapy patients are mostly postoperative, as the Yellow Emperor’s Classic of Internal Medicine says: “If the righteousness exists within, evil cannot dry up”, the patient’s postoperative vital energy is weakened, the spleen and stomach are not able to exercise, the evil is stagnant in the middle, the qi is blocked and inaccessible, the dampness and turbidity are contained within the intestines, the circulation of local qi and blood is obstructed, the qi and blood are not enough to moisten the meridians, so the evidence before radiotherapy is mainly spleen deficiency and dampness. Therefore, the treatment is to strengthen the spleen, benefit the qi and dispel dampness. In addition, the radiation burns the intestinal ligaments and makes the diarrhea fierce, with a large loss of water and fluid in a short time, which eventually leads to the depletion of gastric yin and intestinal fluid. As the disease progresses, the patient’s intestinal ligaments are damaged, rotten flesh and blood are defeated, blood in the stool occurs, spleen deficiency and kidney deficiency, spleen and kidney yang deficiency, five-shift diarrhea occurs, so the treatment is based on nourishing blood and invigorating blood, and tonifying spleen and kidney. We take oral discriminative tonics according to the physical dialectic of patients before radiotherapy, and there exist different types of evidence. With the implementation of radiotherapy plan and increase of dose, the evidence type of patients may change, and timely adjustment of prescriptions according to the evidence type can effectively reduce the incidence of radiation enteritis and the degree of radiation damage to the intestine, and the cure rate and overall efficiency of acute radiation enteritis are significantly better than traditional western medical treatment methods. We hope that patients with pelvic radiotherapy will come to see us as soon as possible to reduce the toxic side effects of radiotherapy and make radiotherapy go smoothly.