Anticoagulants need to be taken for 3~6 months after the filter is removed, and patients at high risk of lower extremity venous thrombosis need long-term anticoagulant medication. Filters are mainly used in the treatment of the inferior vena cava to prevent venous thrombosis from blocking the pulmonary artery. Routine anticoagulation is needed for 3~6 months after removal of the filters to prevent venous thrombosis from forming again, and the exact duration of treatment varies from patient to patient. Some patients may have high risk factors for lower extremity venous thrombosis, such as lower extremity braking, long-term bed rest, hypercoagulable state, etc., which is a high risk group for the occurrence of pulmonary embolism. If the risk factors can not be removed, long-term oral anti-inflammatory drug treatment may be needed to prevent the occurrence of pulmonary embolism. Patients with lower extremity venous thrombosis should evaluate the risk and decide on a specific course of anticoagulants under the guidance of a physician.