Abstract: microRNAs（miRNAs） are a class of noncoding RNAs that are believed to play important roles during tumorigenesis and cancer metastasis. Cancer stem cells are a major source leading to tumor recurrence， metastasis and drug resistance. Researches reported that miRNAs could promote or inhibit the stemness of cancer stem cells， regulate the differentiation and selfrenewal process of cancer stem cells. The purpose of this paper is to describe the phenotype and regulation mechanism of miRNAs in cancer stem cells， and explain its potential role in tumor diagnosis and treatment.