Abstract: Different amounts of DNA or RNA molecules exist in the mammalian blood circulation and in body fluids. These have gained increasing attention in recent years due to the role of circulating microRNA ( miRNA ) in the diagnosis and prognosis of diseases. Currently, reliable prognostic factors of liver diseases, including hepatocellular carcinoma ( HCC ) and hepatitis, are urgently needed. Although the metabolic pathway of circulating miRNA remains unclear and the detection method needs further improvement, the present findings prove that there is a close correlation between the changes of the circulating miRNA and the occurrence and progression of the pathological changes in the liver. At the same time, part of the circulating miRNA labels may be used as molecular markers to evaluate the diagnosis and prognosis of liver diseases. Circulating miRNA detection has its own characteristics, such as it being non-trauma and repeatable, thus determining its broad prospects in evaluating the diagnosis and prognosis of liver tumors and various viruses or metabolic liver diseases. In the present paper, the method of circulating miRNA and its stability were preliminarily introduced. The development in studies regarding circulating miRNA used as diagnostic markers of HCC or liver diseases in China and overseas is systemically recommended to pave the way for further research.