Because heparin sodium has strong negative charge of physical and chemical characteristics, can interfere with many aspects of the process of blood coagulation, in vivo and in vitro have anticoagulant effect. Its mechanism is complex, mainly through and antithrombin Ⅲ (AT - Ⅲ), and enhance the latter to activate Ⅱ a and Ⅹ a, a, Ⅸ Ⅺ a and Ⅻ a clotting factor inhibition. The consequences involve preventing platelet aggregation and destruction and interfering with the formation of clot-activating enzymes; Preventing prothrombin from becoming thrombin; Inhibits thrombin, thereby preventing fibrinogen from becoming fibrin. And tissue coagulation live Ⅲ (factors). Inhibit platelet aggregation and release.