MicroRNAs (miRNAs) are a class of small regulatory RNAs, which repress gene expression at the posttranscriptional levels through binding to target mRNAs for directly cleaving mRNAs or inhibiting protein translation. Mature miRNAs are produced from miRNA genes by multiple biological processes, in which several important enzymes are involved in. To date, several hundreds of miRNAs have been identified in plants using a various computational and/or experimental approaches. These miRNAs regulate plant tissue differentiation, development and growth, control auxin signal transduction, involve in plant response to a variety of abiotic and biotic environmental stresses.