Abstract: MicroRNAs，a class of non-coding small RNAs with 22-25 nucleotides，regulate gene expression at the post-transcription level or translational level. MicroRNAs play important roles in multiple biological processes，including cell differentiation，proliferation and apoptosis，tissue self-renewal，metabolism and cell lifespan. It was reported that microRNAs expressed in oocytes at different development stages, and that microRNAs play important roles in ovarian follicular development and oocyte maturation through regulating gonad development，steroid hormone synthesis，ovulation and luteal formation. It is true that the expression of microRNAs is important for the normal follicular growth and development. The effects of microRNAs on follicular development were reviewed.

Key words: MicroRNAs, Ovarian follicle, Oocytes, Genes