The sequelae after lower extremity venous thrombosis mainly refer to the sequelae of lower extremity deep vein thrombosis. Lower limb deep vein thrombosis, if not treated in time, may cause more serious complications and sequelae. The most common ones are the following three: i. Pulmonary artery embolism, which is the most serious complication of lower extremity deep vein thrombosis. It is due to thrombus dislodgement, and larger thrombus dislodgement can directly cause sudden death of the patient. To prevent such complications, the patient should be strictly bedridden for two weeks after the onset of the disease and avoid exercise. Second, inferior vena cava obstruction syndrome, such as after the upward development or extension of deep vein thrombosis in the lower extremities, may involve the inferior vena cava. It leads to the formation of inferior vena cava thrombosis, which will eventually induce inferior vena cava obstruction syndrome. Third, post-DVT syndrome of lower limb, although the symptoms of lower limb DVT have improved after treatment. However, long-term venous reflux obstruction will also form superficial varicose veins, lower leg skin pigmentation, sclerosis, and even ulcer formation for a long time. This kind of patients is the distant sequel of lower limb deep vein thrombosis, the incidence is about 10%, which needs timely and regular treatment.