Deep vein thrombosis is an abnormal clotting of blood in the deep venous cavity, blocking the venous cavity and leading to venous return obstruction, which may be complicated by pulmonary embolism (fatal or non-fatal) in the acute phase if left untreated, and in the later phase by post-thrombotic syndrome, affecting life and work ability. Deep vein thrombosis of the lower extremities is the most common. The main etiology is venous injury, slow blood flow and hypercoagulable state of blood. Other high-risk factors include pregnancy, perinatal period, prolonged bed rest, surgical braking, and malignancy. The main manifestation is sudden swelling of one limb with pain and superficial varicose veins. In severe cases, the lower limb is highly swollen and venous gangrene of the lower limb may occur. The left lower extremity is more frequently affected. Ultrasound and phlebography may assist in the diagnosis. Treatment includes 1. non-surgical treatment (anticoagulation; thrombolysis; inhibition of platelet aggregation; symptomatic management of swelling, appropriate body position, etc.). 2. surgical thrombectomy. During thrombolysis and anticoagulation, we should be alert to serious complications such as cerebral hemorrhage, and coagulation must be monitored regularly to achieve the best effect of thrombolysis and anticoagulation and to avoid complications such as bleeding. Because of the risk of dislodgement of deep vein thrombus, once the thrombus is dislodged and eventually enters the pulmonary artery with blood flow, a large thrombus may cause extensive pulmonary embolism and sudden death. Therefore, if necessary, an inferior vena cava filter needs to be placed to prevent fatal pulmonary embolism.