In life, most patients don’t pay much attention to the sudden swelling and pain of lower limbs, not knowing that this is the typical performance of lower limb deep vein thrombosis. If not timely and effective treatment, pulmonary embolism may occur life-threatening. In the later stage, deep vein obstruction or venous valve insufficiency is often left in the lower limbs, leading to swelling and ulcers in the lower limbs, which seriously affects the work and life. In the mid-nineteenth century, famous German pathologists have pointed out that the three major causes of deep vein thrombosis (DVT) in the lower limbs are: 1) blood flow stagnation; 2) damage to the blood vessel wall; and 3) hypercoagulability of blood components. In the elderly, sedentary behavior, prolonged bed rest, trauma, surgery, as well as pregnancy and gestation, cerebral infarction stroke, etc. are the main reasons for the development of this disease. The incidence of this disease increases with age. If a venous thrombus is dislodged, it can cause obstruction of the pulmonary artery and its branches, interrupting the blood flow to the corresponding blood-supplying lung tissues, i.e. pulmonary embolism. The clinical manifestations of pulmonary embolism are varied, and the severity of the symptoms is mainly determined by the location and extent of the vascular blockage and the underlying state of the heart and lungs. In mild cases, there may not be any symptoms; in more severe cases, cough, chest pain, difficulty in breathing, etc., and in severe cases, shock or sudden death may occur. Therefore, for patients with lower limb swelling, if the above symptoms occur, do not take it lightly, and should quickly go to the vascular surgery department.