About 90% of the local recurrence of breast cancer occurs in the area adjacent to the primary tumor, and the recurrence in other parts of the breast only accounts for 1%-3%, which requires us to emphasize the importance of partial breast irradiation in the area adjacent to the primary tumor when doing breast-conserving surgery, especially for some low-grade malignant patients, it is worth exploring whether it is necessary to carry out routine whole-breast radiotherapy after surgery. It is also a pity that some patients give up breast conservation or radiotherapy due to busy work schedule, inconvenient transportation, old age and inability to adhere to 5 weeks of radiotherapy, thus increasing the chance of recurrence. How to find an alternative to whole breast radiotherapy that is precise in irradiation site, time-saving, cost-saving and equivalent, intraoperative radiotherapy tries to solve this problem.