Abstract: MicroRNA, also known as miRNA, is a class of noncoding small-molecule RNAs in eukaryotic cells which plays a major role in the post-transcriptional level of target-gene regulation. MicroRNA is involved in the regulation of life processes, such as cell growth, development, differentiation, proliferation, and apoptosis, and affects almost all of the signaling pathways involved in various physiological and pathological processes. It also plays an important regulatory role in the development and progression of tumors. The relationship between microRNA and cancer research has recently gained much attention. The impact of microRNA on the body, particularly its immunological anti-tumor mechanisms, and the major breakthrough in the diagnosis and treatment of cancer provide new ideas. In the current paper, the biological function and anti-tumor immune mechanisms of microRNA were reviewed.