Acute coronary syndrome (ACS) is a clinical syndrome with atherosclerotic plaque rupture as its main pathological manifestation. Inflammatory response plays an important role in this process. Various immune cells, cytokines and inflammatory mediators participate in and promote the occurrence and development of inflammatory response. In recent years, it has been reported that regulatory T cell (Treg) is a kind of special CD4＋ T cell which can negatively regulate immune function. The number and proportion of Treg in human body have a certain impact on the occurrence and development of autoimmune diseases such as rheumatoid arthritis, mandatory spondylitis and systemic lupus erythematosus. At present, most related studies have confirmed the correlation between Treg and ACS. This review will focus on the origin, biological characteristics of Treg, the relationship between Treg and ACS, and the possible mechanism.