I. Introduction
miRNA is a kind of small non-coding RNAs [1], which regulates gene expression by binding to target mRNA and participates in a variety of biological processes, including cell differentiation, proliferation, apoptosis and so on [2]. miRNA family is a group of miRNAs that derive from the common ancestor [3]. The classification of miRNA families helps to deeply understand the diversity and functions of miRNAs and is of great significance for understanding the regulatory mechanisms of life processes. Studies about the classification of miRNA families provided a better understanding of the pathogenesis, diagnosis, treatment and prognostic assessment of diseases [4].