Long-term anticoagulation in pulmonary embolism has been an important issue in the clinic. Although newer anticoagulants are available, warfarin, the oldest oral anticoagulant, is still the most commonly used drug for patients requiring long-term anticoagulation therapy. Patients need to understand the following knowledge during long-term oral warfarin. 1, drug mechanism of action Warfarin is an oral vitamin K antagonist (VKA), through the inhibition of hepatic epoxide reductase, so that the inactive oxidized (epoxide type) VK can not be reduced to active reduced (oxyquinone type) VK, prevent the circulating application of VK, interfere with the carboxylation of VK-dependent coagulation factor II, VII, IX, X, so that these coagulation factors can not be activated, only stay in the precursor phase, and the anticoagulant purpose is achieved. Warfarin has good oral bioavailability with a half-life of 36-42 hours. It is mainly bound to albumin in plasma, almost completely metabolized by the liver, excreted mainly by the kidneys, and rarely enters the bile, and only a very small amount of warfarin is excreted in its original form in the urine. The dose-effect relationship of warfarin is influenced by genetic and environmental factors. Drugs, diet, and various disease states can alter the pharmacokinetics of warfarin. Therefore, patients taking warfarin should be monitored intensively for PT-INR when adding or discontinuing any medications, including herbal medicines. pautazone and metronidazole can significantly enhance the effect of warfarin on prothrombin time (PT). In contrast, cimetidine and omeprazole only mildly enhance the effect of warfarin on PT. Chronic alcohol consumption increased warfarin clearance, but consumption of large amounts of wine had almost no effect on PT in patients. Patients taking warfarin should avoid concomitant administration with non-steroidal anti-inflammatory drugs and avoid concomitant administration with anti-platelet drugs unless the benefit outweighs the risk of bleeding. 2, pay attention to bleeding adverse reactions The application of warfarin for long-term anticoagulation therapy requires attention to monitoring PT-INR and paying attention to its bleeding adverse reactions. Anticoagulation therapy can increase the risk of bleeding complications in patients, so care should be taken to assess the patient’s bleeding risk before and during treatment, and to determine the appropriate treatment plan. The incidence of bleeding events due to warfarin varies by treatment population. Minor bleeding may include nosebleeds, gum bleeds, skin and mucosal bruises, and menstrual cramps; severe bleeding may include hematuria, gastrointestinal bleeding, and, in the most severe cases, intracranial bleeding. The risk of bleeding in patients taking warfarin is related to the intensity of anticoagulation, but also to whether the patient is on initial or long-term anticoagulation and whether coagulation is monitored. In addition, the most important bleeding risk factors associated with patients are history of bleeding, age, tumor, hepatic and renal insufficiency, stroke, alcohol abuse, and combined medications. 3. Strengthening the management of warfarin anticoagulation therapy Although warfarin has many limitations and dose adjustment and monitoring are cumbersome, patient follow-up and education through specialized clinics and systematic management can significantly enhance patient compliance and medication safety. Therefore, the Chinese expert consensus recommends the establishment of specialized outpatient clinics in hospitals where available to enhance anticoagulation management for patients on long-term anticoagulation therapy. Monitoring INR as required is an important measure to ensure safe and effective anticoagulation therapy for patients. Patients should be managed systematically, integrating patient education, systematic INR monitoring, follow-up visits and good communication with patients. To this end, our professionals will inform patients of the following precautions when they are discharged from the hospital: 1) The medication should be taken only once a day, preferably at the same time in the evening. 2) To facilitate monitoring, the dose of warfarin should be recorded at the time of each dose. (3) Please make up the dose within 4 hours after forgetting to take the medication, do not make up the dose after 4 hours, and continue to take the medication normally on the second day, and do not double the dose on the second day because you forgot to take the medication. If you do not take the medication twice in a row, please contact your doctor promptly. 4) You should not stop taking anticoagulant medication at random. 5) If you change to another size or manufacturer of medication, please consult your doctor first. 6）The following are some serious warnings of bleeding, once they occur, please go to a nearby hospital as soon as possible: ① severe and prolonged headache; ② bleeding when vomiting; ③ abdominal swelling; ④ red color in urine or black color in stool; ⑤ severe bleeding from the eyes.