Deafness has become one of the most frequent health problems worldwide, and affects almost every age group. Hair cell damage or absence is the main cause of hearing loss, but there is no successful treatment to heal deafness. MicroRNA (miRNA), as a highly conserved endogenous non-coding small RNA, plays an important role in inner ear cochlea and hair cell development. In this review, we elaborate on the expression and function of miRNAs in cochlear hair cell development, and reveal its indispensable important role. We summarize the molecular mechanism of miRNA in regulating transcription factors involved in cochlear hair cell development, which may provide references and insights for hair cell regeneration in vivo and cellular transplantation therapy of deafness.