1.Non-hazardous It is more suitable for young women, especially pregnant and lactating women, and it is more convenient to conduct screening and follow-up. 2.Identify the physical nature of tumor It is of great value to identify cystic or solid breast tumors, and ultrasound can detect 2mm cysts. 3.Ultrasound can clearly show the anatomical level of breast and subtle lesions, so as to give clear localization of lesions. 4.Ultrasound can clearly show whether there are enlarged lymph nodes in the axilla and supraclavicular area, and can also characterize whether there is metastasis, mainly depending on whether there is a lymphatic gate, whether the medullary structure is destroyed, and the richness of blood flow. Especially in obese patients, when clinical diagnosis is difficult, ultrasound can provide the size and location of the enlarged lymph nodes. Problems: It is not clear for very small fine calcifications. It is still difficult to differentiate between inflammatory breast masses and inflammatory breast cancer. High-frequency ultrasound examination of the breast has the advantages of being economical, easy, painless, non-invasive, and easily accepted by patients. As long as it is used properly, the examination of breast diseases can complement each other with X-ray mammography, and can be used as the main means of early diagnosis of breast tumors.