Abstract: MicroRNAs(miRNA)are 20~25 nucleotides small non-coding RNA molecules.miRNAs exert their functions by gene silencing either via mRNA degradation or preventing mRNA from being translated or by post-transcription.With the rapid advance in next generation sequencing technology and bioinformatics,abundant miRNAs have been identified,some of which have been functionally analyzed.Here,we review the research progress at genome level as well as in different biological processes,e.g.rhizobia symbiosis,grow development and flowering,biotic and abiotic stress.