Pulmonary embolism, as the name implies, is an obstruction of pulmonary circulation caused by an embolus blocking the pulmonary artery, mainly manifesting as chest tightness, chest pain, hemoptysis, shock or even sudden death, with high clinical misdiagnosis and mortality. There are various emboli causing pulmonary embolism, including blood clots, fat, amniotic fluid, air or tumor emboli, etc. The most common one is the obstruction of pulmonary artery or its branches by thrombus from deep venous system such as lower limb or pelvic vein. It has been found that pulmonary embolism is not uncommon in clinical practice, but the lack of specificity of symptoms often leads to clinical misdiagnosis or underdiagnosis. Pulmonary embolism and deep vein thrombosis are diagnosed in approximately millions of patients worldwide each year. Nearly 300,000 fatal pulmonary embolism deaths occur each year in the United States, with approximately 60% of these patients being underdiagnosed and only 7% receiving timely and correct diagnosis and treatment. Research has found that there are many risk factors for pulmonary embolism in addition to a genetically related predisposition to thrombosis. Age greater than 75 years, obesity, pregnancy, oral contraceptives, oncology patients, and pacemaker implants are all at high risk for pulmonary embolism. The chance of venous thrombosis in obese patients is 2 to 3 times higher than that in normal population; the chance of venous thrombosis in tumor patients is 5 times higher than that in non-tumor population. In addition, bed rest and reduced limb activity due to varicose veins, or surgery or trauma are also high risk factors for venous thrombosis. Travelers, because of long time travel by airplane, train or car, sit quietly in a small space, the venous reflux of both lower limbs slows down and blood flow stagnates, thus deep vein thrombosis or pulmonary embolism occurs, also known as economy class syndrome. Patients with pulmonary embolism above may not have any symptoms, so they are easily ignored clinically. The symptoms of symptomatic patients also lack specificity, depending on the size and number of emboli, the site of embolism and the presence of underlying cardiac and pulmonary disease. Smaller emboli may not have any clinical symptoms. Larger emboli can cause dyspnea, syncope, and sudden death. Sometimes syncope may be the only or the first symptom. Pulmonary infarction may be manifested by chest pain, hemoptysis and dyspnea, which is clinically known as “pulmonary infarction triad”. Common tests used to diagnose pulmonary embolism include plasma D-dimer, CT pulmonary angiography, isotope ventilation and perfusion scan, echocardiography and deep vein ultrasound of the lower extremities, and pulmonary angiography if necessary. The treatment of pulmonary embolism is based on anticoagulation. For large pulmonary embolism or sub-large pulmonary embolism causing shock, thrombolytic therapy should be given with the premise of controlling the risk of bleeding. Given the high mortality rate of pulmonary embolism, prevention of the disease becomes even more important. The primary measure is to increase blood flow velocity to the extremities and reduce blood stasis in the lower extremities, thereby reducing venous thrombosis. For the elderly, obese people, tumor patients and other people with high risk factors for thrombosis, they should move around frequently and not stay in a fixed sitting position for too long. Long-distance travelers should get up regularly to move their lower limbs and not sit for a long time; when sitting in long-distance airplane or other transportation, untie the shoelaces or wear slippers, which can reduce the pressure on the local blood vessels of ankle and reduce the edema of lower limbs. Patients with varicose veins can wear compression elastic stockings and sit down regularly to elevate their legs after standing for a long time, which is conducive to blood return to the lower limbs. For those who must be bedridden for a long time after trauma or surgery, they can use compression elastic stockings or elastic bandages, do inflatable massage of lower limbs regularly, and also do preventive anticoagulation therapy under the supervision of doctors; meanwhile, they can urge patients to turn over regularly, and those who can move on their own but cannot get out of bed, try to move the knee and ankle joints of lower limbs by themselves and take the initiative to do muscle exercise; for those who cannot move on their own, their family members should do muscle massage of limbs daily. This can accelerate the venous blood flow in the lower limbs, which is effective in preventing deep vein thrombosis in the lower limbs. If there is asymmetric swelling of the lower limbs, we should pay attention to it and take the initiative to go to the hospital for further examination.