Activin is a member of the transforming growth factor-beta (TGF-beta) superfamily that result from the assembly of disulphide-linked betaA and betaB subunits. Activin receptors are transmembrane proteins and activin fulfils the biological function through the signal transduction of the receptor system. In recent years, many studies have suggested that activins have wide biological activities. It is the basic medium in regulating histiocytic function and plays a role in maintaining the normal function of cells. Moreover, abnormal expression of activin in the tissues of many gynecologic and obstetric diseases, such as epithelial ovarian tumor, endometrial carcinoma, pre-eclampsia, polycystic ovary syndrome, endometriosis and so on affects the development of these diseases.