Abstract: Cardiovascular disease is one of the major diseases that cause death and disability in the world. Due to unobvious early clinical manifestations, this disease is likely to be ignored, leading to rapid progress and poor prognosis. Novel therapeutic approaches of diagnosis and treatment have become the research focuses in this field. MiR-21, as one of the abundantly expressed and highly conserved microRNAs, plays a key regulatory and intercellular messenger role in the pathophysiological progression of diseases. It has been confirmed that miR-21 is highly expressed in cardiac tissue and is essential for maintaining cardiac homeostasis. This paper summarizes the research progress of miR-21 in cardiovascular diseases by taking cardiomyocyte apoptosis, lipid metabolism and myocardial fibrosis as the breakthrough points, and discusses its application prospects and challenges as a specific diagnosis and treatment target.