The preparations that must be made before radiotherapy for rectal cancer include psychological construction, understanding whether there are contraindications to radiotherapy, side effects of radiotherapy, reasonable diet and ensuring sufficient rest. Radiotherapy is an important part of comprehensive treatment for rectal cancer, and patients can prevent tumor recurrence with radiotherapy after surgery. For patients who cannot be operated, radical radiotherapy can be carried out, which can control the development of the disease or get the chance of surgery, which is beneficial to promote the recovery of the disease. However, before radiation therapy, patients need to do sufficient psychological construction, keep optimistic and positive mood, and avoid negativity, anxiety and tension. At the same time, they can eat foods with high quality protein appropriately, increase the intake of fresh fruits and vegetables, and avoid eating excessively greasy foods. Keep sufficient rest time and avoid overwork. After receiving radiation therapy, patients with rectal cancer should also take into account their own conditions and follow the doctor’s instructions for regular review so as to understand the recovery of the disease.