Anticoagulants are divided into in vivo and ex vivo anticoagulants, heparin class, such as ordinary heparin, low molecular heparin, etc.; in vivo anticoagulants, coumarin class, such as warfarin; ex vivo anticoagulants, such as sodium citrate; and new type of anticoagulant, such as dabigatran and rivaroxaban. 1. In vivo and ex vivo anticoagulants: heparin class, such as ordinary heparin, low molecular heparin, both in vivo and ex vivo have powerful anticoagulant effect, used for antiphospholipid syndrome, anticoagulation during pregnancy, sealing of all kinds of tube placement operations. 2. In vivo anticoagulants: Coumarins, such as warfarin, reduce the synthesis of vitamin K-related coagulation factors, used in myocardial infarction, deep vein thrombosis and prevention of postoperative thrombosis. 3. In vitro anticoagulants: such as sodium citrate, mainly competitive binding of calcium ions to prevent blood coagulation, used for blood storage and transfusion of anticoagulation, is the main component of blood bank maintenance fluid. 4. New anticoagulants: such as dabigatran and rivaroxaban, which are potent, competitive, reversible, direct thrombin inhibitors, and can be used for anticoagulation treatment of atrial fibrillation and other diseases. Therefore, there are several kinds of anticoagulants, and patients should use them reasonably under the guidance of specialists, avoiding blind use of medication by themselves to avoid adverse reactions.