Angiogenin is a group of secreted cytokines that play an important role in revascularization, embryonic vascular, and cancer. There are four members in the family of angiogenin: Ang-1, Ang-2, Ang-3 and Ang-4, which have different functions in biological processes. Ang-1 inhibits endothelial cell apoptosis and promotes endothelial cell survival by activating its receptor tyrosine kinase Tie-2. The amino acid composition of Ang-1 and Ang-2 is partly identical and has a similar structure. Ang-2 participates in angiogenesis, remodeling and endometrial destabilization. The structure of Ang-3 cloned from mouse and Ang-4 cloned from human differed greatly from Ang-1 and Ang-2. Functionally, Ang-3 is similar to Ang-2, which acts as an antagonist. Agn-4 is similar to Ang-1, which acts as an activator.