Breast cancer is one of the common malignant tumors in women. Surgical removal of the tumor, chemotherapy, radiation therapy, endocrine therapy, and targeted therapy are the main treatment options for breast cancer treatment. Traditionally, the surgical procedure is to remove the entire breast. However, with the development of medicine, breast-conserving surgery is gradually promoted, which can ensure a good breast shape and improve women’s self-confidence and quality of life. Nowadays, breast-conserving surgery has become the preferred international and domestic breast cancer surgery method. Breast cancer patients need to receive radiation therapy after undergoing breast-conserving surgery. After surgery, the affected side of the breast is irradiated using high-energy X-rays; typically 25 to 30 times; and the treatment is completed in about 5 to 6 weeks. Post-operative radiation therapy is part of the treatment to preserve the breast; it can further control the malignancy and reduce the risk of recurrence. The side effects are mainly mild skin reactions within the radiation range, which usually recover about 2 weeks after the end of treatment; the incidence of other toxic effects is very low. In addition, it should be pointed out that patients who receive radiation therapy are not radioactive themselves and will not affect surrounding family members or children.