Abstract: Circlar RNAs(circRNA)is one kind of endogenous non-coding RNA molecule,which is formed by 5' cap structures and 3' poly(A)tails covalently bonding to form a closed loop structure.It can be divided into exonic cir-RNAs,cirRNAs and exon-in-troncircRNA(EIciRNA)according to the different splicing sources of circular. In this study,the research status and biological functions of circRNA were reviewed from the aspects of molecular characteris-tics,research process,formation process,mechanism of action,database and analytical tools.The review indicated that, with the progress of high-throughput sequencing technology and the rapid development of bioinformatics,more and more circRNA were discovered.circRNA had the characteristics of stability,universality,conservatism and tissue specificity.It played an important role in gene expression regulation.It could be used as a biomarker for certain diseases,and enjoyed broad application prospects in clinical diagnosis and treatment. However,many important biological functions of circ-RNA remained unknown,such as its mechanism of action in villus growth and development.The studies in disease diag-nosis and treatment needed to go deeper.Therefore,in future research,intensive study should be made in circRNA and its mechanism of action in disease diagnosis,treatment and villus development to fully understand its biological functions, so that it can be widely used in various fields.