Early diagnosis of pulmonary embolism, correct judgment of the disease and post-treatment have significant impact on the prognosis. The current clinical examination and diagnosis of pulmonary embolism are mainly based on the patient’s symptoms, signs and past medical history as well as laboratory tests to confirm the diagnosis, as follows: 1. Patients with pulmonary embolism may have hypoxemia, but normal blood gas results cannot exclude pulmonary embolism, and hypoxemia combined with hypocapnia can increase the suspicion of pulmonary embolism. 2. D-dimer: D-dimer is a degradation product of cross-linked fibrin. Therefore, in cases of pulmonary embolism and deep vein thrombosis, D-dimer is higher than normal, but it may also be elevated in cases of tumor, inflammation, infection, necrosis, aortic tear, hospitalization, or pregnancy; 3. Pulmonary arteriography: It is the currently accepted gold standard for the diagnosis of pulmonary embolism.