Cyclin G1 is a new member of the Cyclin G family, while it is not the main molecule for regulating cell cycle functionally. Cyclin G1 has been found to play important roles in the replication of hepatitis viruses and development of hepatocelluar carcinoma(HCC). This paper aims to review the research progress on the characteristics of Cyclin G1 protein sequence, the interaction of Cyclin G1with microRNA, the roles and mechanisms of Cyclin G1 in the replication of HBV and HCV as well as the development of HCC, which might provide the theoretical basis and new research insights for the related diseases.