Objective To summarize the research progress of microRNA （miRNA） as a tumor marker in peripheral blood. Methods The domestic and international published literatures about circulating miRNA as a tumor marker in recent years were reviewed. Results The miRNA expression has universality，stability and specificity，and it is related to the occurrence and development of viarous diseases. Conclusion Circulating miRNA shows a broad application prospect in clinical diagnosis， treatment， and prognosis of tumor and other diseases.