microRNA (miRNA), an abundant class of 22nt highly conversed, small noncoding RNA, can make mRNA degradation or influence mRNA translation via a complementary with the 3’-UTR of the miRNA. Recently, more studies show the effects of these noncoding small RNAs on immune system development and response, and miRNA is involved in the regulation of immunity, including the development and differentiation of immune cells, antibody production, in?ammatory mediator release and signal transduction in cells. miRNA is considered to play roles in maintaining the homeostasis of immune system and immune-associated diseases. Here, the latest ?ndings are summarized to explore the function and mechanism of miRNA in modulating innate and adaptive immune responses.