Breast cancer is a common tumor in women.Early and timely diagnosis is crucial for treatment and prognosis.As a routine method of breast examination,ultrasonography plays an important role in diagnosis of breast diseases.Superb microvascular imaging (SMI) is a new ultrasonic blood flow imaging technique in recent years,which separates spectrum signals of low-speed flow from normal tissue motion by an adaptive algorithm.SMI can display the slow-speed flow more realistically,and has been used on breast,thyroid,liver and so on.SMI is obviously valuable in clinic.The principle and application progresses of SMI in diagnosis of breast diseases were reviewed in this article.