Rheumatoid arthritis (RA)is a common autoimmune disorder characterized by polyarticular. Clinical treatment is based on the degree of disease activity In the meantime disease activity is an important index to evaluate the power of medicines and course of disease， At present， disease activity score 28（DAS28）is most commonly used to assess the disease activity，however， the score has a certain subjectivity and computing DAS28 is time-consuming， requires laboratory testing and an online calculator ，so it is not convenient for clinicians， especially clinic doctor. In recent years， the new techniques of high frequency ultrasound(HFUS) occupies vital position in diagnosis and treatment process of RA. This article review the new technique of HFUS diagnosis in RA disease activity.