MicroRNAs (miRNAs) are one kind of small RNA in all eukaryote.MicroRNAs can regulate gene expression of eukaryote;they widely participate in every physiological process.They can block mRNA expression or cleave mRNA by complement to target mRNA.Scholars estimate miRNA genes occuping about 1% of genome,but they can regulate 10%-30% genes of whole genome.The genes are regulated by miRNA including signal proteins,enzymes,transcription factors,and so on.In the field of plant research,the start of miRNA research is later,but it is proved that plant miRNAs are important to every plant physiological process.Now miRNA has become the hotspot of plant molecular biology research.This paper introduced the biology function,action mechanism,researching method and recently development of microRNAs,also focused on advances in plant microRNAs.This paper has important reference value for plant stress tolerance miRNA research.