Pulmonary infarction is caused by embolism of the pulmonary artery due to an embolus from outside the lungs, which in turn causes hemorrhage and necrosis of the lung tissues, and in severe cases it can be life-threatening. Its cause can be the factor of age, the older the relatively higher the risk. Secondly, less activity, prolonged inappropriate bed rest, or reduced limb activity in healthy people usually reduces the driving force of venous blood flow, leading to venous blood stagnation and easy formation of thrombosis in deep veins. Varicose veins and thrombophlebitis can also cause pulmonary embolism. Cardiopulmonary diseases, especially atrial fibrillation with heart failure, are more prone to pulmonary embolism, and soft tissue trauma as well as extensive burns can also occur. Some tumors, such as lung cancer, stomach cancer, pancreatic cancer, etc., can be complicated by pulmonary embolism, and long-term use of oral contraceptives can also be induced. Other causes such as erythrocytosis, diabetes mellitus, and pulmonary embolism can also be triggered.