Coagulation factor IX, also known as FIX and F9, is a serine protease belonging to the peptidase family S1. F9 is produced as an enzyme precursor and non active precursor, followed by a series of processing processes; Remove signal peptides, glycosylation, and then cleave into a double stranded form connected by disulfide bonds by factor XIa or factor VIIa. Antithrombin can inhibit F9. In addition, the expression level of F9 increases with age in humans and mice. Lack of F9 can lead to the occurrence of type B hemophilia. Among over 100 F9 mutants, some do not cause any symptoms, but many can cause significant bleeding disorders. Recombinant F9 can be used to treat hemophilia type B, with BeneFIX and Alprolix available on the market. Some rare F9 mutations can lead to increased coagulation activity, leading to coagulation diseases such as deep venous thrombosis. Patients with congenital deficiency of F9 may experience a reduced risk of perioperative bleeding when undergoing surgery with tranexamic acid.