Since its introduction in the 1940s, warfarin (warfarin) has been widely used in clinical prevention of thromboembolic diseases and prevention of acute heart attack, stroke, and reinfarction in high-risk patients because of its irreplaceable nature. Warfarin is inexpensive, has high bioavailability, has a real oral antithrombotic effect, is mainly absorbed in the gastrointestinal tract, metabolized in the liver, and acts by interfering with the circulation of vitamin K in the body. However, due to numerous influencing factors and individual differences, the effective dose of safe dosing varies from patient to patient. Therefore, to ensure the effectiveness of antithrombotic therapy and patient safety, patients should be aware of the diseases, drugs and foods that interfere with the efficacy of warfarin, pay attention to their health status, combined medications and dietary structure, and monitor the coagulation index “International Normalized Ratio (INR)”. Generally speaking, the normal range of INR is 0.8-1.2. If, for various reasons, thromboembolic disease may occur or has occurred in patients within the normal range of INR, it is necessary to take Warfarin to exert thrombotic effects to bring the INR from normal values to the target value that can exert antithrombotic effects. The target value of INR for national population is 2-3; INR below 2 cannot exert effective antithrombotic effect, and INR above 3 increases bleeding events. Warfarin has no side effects except for possible allergy and bleeding in case of overdose, and it is safe to monitor the INR within the target value when the condition requires long-term administration.