Abstract: miRNAs are small RNAs of 18-25 nt in lengths discovered in recent years. They do not encode mRNAs,but play important regulatory roles in the transcriptional or post-transcriptional level of genes and control many biological processes including growth, differentiation, metabolism and disease. In recent years, studies have shown that miRNAs play an important role in the regulation of mammal reproduction. The abnormal expression of miRNAs is closely related to various genital diseases and leads to the decline of fecundity and even Infertility. This article summarizes the discovery, biosynthesis, working mechanisms of miRNAs as well as research progress in animal reproductive performance. It will provide reference for the further study of miRNA.