Pulmonary embolism (PE) is the most common fatal emergency in developed countries such as Europe and the United States, and is the leading cause of death in all age groups. The mortality rate of pulmonary embolism in the United States ranks 3rd after malignancy and myocardial infarction, with at least 650,000 patients dying from pulmonary embolism each year. In the United Kingdom, the annual incidence rate is 600-70 per million and the annual mortality rate is 1 per 10 million. Pulmonary embolism is a clinical and pathophysiological syndrome caused by endogenous or exogenous emboli blocking the pulmonary artery and causing pulmonary circulatory disorders, and pulmonary hemorrhage or necrosis caused by pulmonary embolism is called pulmonaryinfarction. The clinical manifestations can range from asymptomatic to hemoptysis and even sudden death, and the symptoms are related to the size of the embolus, the rate of embolism and the underlying cardiac and pulmonary function. In the United States, autopsy studies have shown that about 60% of unexplained deaths in hospitalized patients are due to pulmonary embolism, and the misdiagnosis rate is as high as 70%. Pulmonary embolism has been regarded as a rare disease in China, but in the past 10 years, clinical epidemiological surveys have shown a steady increase in the number of cases, which should cause clinical vigilance.