Pulmonary embolism is a serious complication caused by the blockage of one of the pulmonary arteries by an embolus, most commonly from a thrombus in the venous system. When embolism produces a severe blood supply disorder, necrosis of the lung tissue can occur, which is called pulmonary infarction. It is a common cause of acute lung disease. Clinical signs and symptoms are often nonspecific and quite variable, making them difficult to distinguish from other cardiovascular diseases. Although the severity of symptoms is related to the size of the embolus and the extent of embolization, it is not necessarily proportional and often closely related to the compensatory capacity of pre-existing cardiac and pulmonary diseases. (A) Acute massive pulmonary embolism: manifests as sudden onset of severe dyspnea, myocardial infarction-like retrosternal pain, syncope, cyanosis, right heart failure, shock, profuse sweating, cold extremities and convulsions. Even cardiac arrest or ventricular fibrillation occurs and death occurs rapidly. (b) Medium-sized pulmonary embolism: often with retrosternal pain and hemoptysis. Syncope and hypertension can be produced when the patient has poor compensatory function for pre-existing cardiac and pulmonary disease. (iii)Microembolism of the lung: can produce adult respiratory distress syndrome. (iv) Pulmonary infarction: often with fever and mild jaundice. I. Internal treatment. (A) General treatment: The disease has an acute onset and requires emergency treatment. The patient should be kept at absolute bed rest and on oxygen. (B) Anticoagulation therapy. 1.Heparin. 2.Vitamin K antagonist – Warfarin, taken orally. (C) fibrinolytic agents: that is, thrombolytic therapy. Fibrinolytic agents can promote the dissolution of venous thrombosis and pulmonary embolism, restore the obstructed blood circulation, is a safe treatment method. Second, surgical treatment. (a) Pulmonary embolectomy. (b) Vena cava block: mainly to prevent the recurrence of embolism and even endanger the pulmonary vascular bed.