Regular self-examination of breasts can detect abnormal breast conditions in time for timely consultation, which can lead to the detection of some breast diseases, especially early detection of breast cancer. According to statistics, 80% of breast patients are found unintentionally while bathing or changing clothes, and 95% of breast cancers can be detected through self-examination, but most of them are already in stage II or III when symptoms appear, and some of them have already lost the hope of cure. Therefore, we advocate that women should learn to self-examine their breasts to detect and treat breast diseases as early as possible. The best time for breast self-examination is 3~5 days after menstruation or 9~11 days after menstruation. 1, because before menstruation, the breast tissue is affected by ovarian hormones, the breast tissue is hyperplastic and thickened, in a state of congestion, and accompanied by pressure and swelling pain, it is not easy to check accurately at this time, easy to misdiagnose or miss diagnosis; 2, 9-11 days after the start of menstruation or 3-5 days after clean is the least affected by hormones, the glandular tissue is the thinnest, softest period, easy to feel, is the best time to check. This is the best time for examination.