Abstract: MicroRNAs(miRNAs) are endogenous non-coding RNAs, which can degrade their target mRNAs or inhibit their translation by binding to their target mRNAs specifically. MiRNAs act as post-transcriptional regulators of gene expression, and then are involved in diverse physiological activities. Many studies has shown that miRNAs are closely related with radiation carcinogenesis, radiosensitivity, radioresistance and radiation-induced bystander effects, and have being a hotspot in radiation-medicine research. This review focuses on the introduction of miRNAs and their applications in radiation medicine.