In recent years, with the change of detection means and life style, the incidence of breast cancer is getting higher and higher, and the youthfulness is becoming more and more obvious. After receiving surgery, radiotherapy is a very important treatment for breast cancer, and there is radioactive dermatitis in the early stage during radiotherapy. Most of the breast cancer patients have such experience during radiotherapy, in the early stage of radiotherapy, such as radiotherapy several times when the radiotherapy area will have localized redness, swelling, and even some erythema, which is the early skin reaction of radiotherapy. As radiotherapy continues, dry skin reactions such as hyperpigmentation, sweat hair loss, edema, and even more severe wet skin reactions such as peeling and blistering may occur in the radiotherapy area. Early patients with breast conservation therapy after breast edema, swelling and pain is also a common adverse reaction, some patients in the radiotherapy period and after the end of radiotherapy, there will be different degrees of breast discomfort, tugging sensation, pain, edema, especially for women with large breast size, breast edema is more pronounced, anti-inflammatory and symptomatic reduction treatment can be given. Then there are some common hematologic toxicity, during radiotherapy may have an effect on some ribs or some vertebrae, which is one of the blood-producing organs, so hematologic toxicity may occur. Radiation lung injury, also known as radiation pneumonitis, is relatively rare and mild for breast cancer, the chance is very low, not more than 10%, even if the symptoms appear, they are relatively mild, if it affects the patient’s life, such as coughing and shortness of breath, anti-inflammatory, de-puffing, anti-coagulation and other treatments can be given, and most of them can be relieved very soon according to the treatment of radiation pneumonitis. Patients with advanced breast cancer will also have edema of the upper limbs on the affected side, as well as brachial plexus nerve injury, lowering of thyroid function, and cardiovascular disease in the left breast cancer, which are also the adverse reactions in the process of breast cancer radiotherapy. Acute phase reactions can be tolerated, while late phase reactions should be minimized or even prevented.