Circular RNAs (circRNAs) are a novel class of RNA, cyclized by linking the 3′ end of the RNA to the 5′ end to form a covalently closed ring structure without a polyadenylic acid tail. CircRNAs are widely distributed, and can be found in various species and in different subcellular compartments. It has been found that circRNAs are closely related to the occurrence and development of cardiovascular diseases, neurological diseases, cancer and other diseases. Its mechanisms of action include acting as miRNA sponges, interacting with RNA-binding proteins, regulating gene expression, and encoding proteins. This article reviews the biogenesis and functions of circRNAs, and research progress in cardiovascular diseases.