Most of the side effects of 25 times of rectal radiotherapy can be fully recovered in about half a year, and some patients last longer, even about 2 years to recover. Rectal cancer is a relatively common malignant tumor in clinic, and radiotherapy, chemotherapy and surgery are its important treatment modalities. Radiotherapy will produce corresponding adverse reactions, such as radiation dermatitis, enteritis, intestinal perforation, etc. Most of the mild adverse reactions last for 1~1 month and can be gradually relieved, and some patients can recover in about half a year. Most of the mild adverse reactions can be gradually relieved in 1~2 months, and can be fully recovered in about half a year. For severe radiation enteritis, it may last for one to two years, during which time the patient may experience recurrent abdominal distension, abdominal pain, or even blood in the stool. If serious adverse reactions occur right in the middle of radiotherapy, radiotherapy should be stopped in time. Therefore, the duration of side effects after radiotherapy for rectal cancer should be specifically analyzed according to the specific situation of patients, and if there is any discomfort, consult the doctor in time and take active treatment to avoid delaying the condition.