Due to the development of our economy and the improvement of people’s living standard, the incidence of cardiovascular and cerebrovascular diseases and diabetes mellitus has increased greatly. Many patients are treated with anticoagulants applied after surgery. One of the most commonly applied is heparin, which is used to prevent auto thrombosis or contact thrombosis. The average molecular mass of common heparin is about 15 KDa (4 to 30 KDa), mostly above 5 KDa, with comparable anticoagulant effects on factor Xa and IIa. Low molecular heparin is a heparin fragment with an average molecular weight of 4~6.5 KDa generated by chemical or enzymatic depolymerization of heparin in recent years. Because of its small molecular weight, it is not easily neutralized by factor IV released by platelets in thrombosis, and its anticoagulant effect and fibrinolytic effect are enhanced, while its anti-platelet and bleeding-inducing effects are greatly weakened, and its effect on lipid metabolism is minimal, and its bioavailability is as high as 98%. Its anticoagulant effect against factor Xa and IIa is about 2~4:1, so low molecular heparin is more suitable for coronary heart patients with low procoagulant requirements. The antithrombotic effect of heparin is maintained and the risk of bleeding is reduced.