1 .Non-hazardous: It is more suitable for women of childbearing age, especially for pregnant and lactating women, and it is more convenient to conduct screening and follow-up. 2.Identify the nature of tumor: it is of great value to identify cystic or solid tumor of breast, and ultrasound can detect 2mm cyst. 3.Ultrasound can clearly show the anatomical level of the breast and the subtle lesions, so as to give a clear localization of the lesions. 4.Ultrasound can clearly show the presence of 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 degree of blood flow. Especially for obese patients, when clinical diagnosis is difficult, ultrasound can provide the size and location of enlarged lymph nodes. 5. It is better for breast with severe hyperplasia. 6.It is not clear for very small fine calcification. 7.The disadvantages can be avoided by combining with mammography.