Pulmonary embolism (PE) is a clinical syndrome in which emboli are formed in the lungs due to multiple causes, resulting in obstruction of pulmonary circulation. The emboli of pulmonary embolism are mainly blood clots, especially in elderly people with chronic cardiology diseases and long-term bedridden, where venous return is blocked and prone to sludge formation of thrombus. The thrombus comes from the deep veins of the lower extremities, fat embolism, air embolism, and metastatic cancer. In previous literature, the most common clinical symptoms of pulmonary embolism are dyspnea, chest pain, and syncope, called the triad, but the triad is often seen in patients with large or multiple pulmonary embolisms. geerts et al. found that most patients with pulmonary embolism have an acute onset, lack specific symptoms, and have a clinical misdiagnosis rate of 60% to 80%. In the Expert Recommendations for the Prevention of Venous Thromboembolism in Hospitalized Patients in Internal Medicine, it was noted that pulmonary embolism has a high mortality rate, with only 32% of pulmonary embolisms diagnosed prior to death and only 45% clinically considered. The researchers selected 99 patients with pulmonary embolism and found that 56 patients (56.6%) had been misdiagnosed during the consultation. The main diseases misdiagnosed: pneumonia in 23 cases (23.2%), tuberculosis in 7 cases (7.0%), left heart failure in 7 cases (7.0%), lung cancer in 3 cases (3.0%), myocardial infarction in 3 cases (3.0%), in addition to angina pectoris, bronchial asthma, pleurisy, myocarditis, interstitial pulmonary fibrosis, acute whistle distress syndrome, acute abdomen, and pulmonary hypertension. The reasons for misdiagnosis were analyzed as insufficient knowledge of pulmonary embolism, failure to perform basic examination, atypical clinical presentation and equipment limitation, and their misdiagnosis rates were 55.6% (55/99), 28.3% (28/99), 7.0% (7/99) and 2.0% (2/99), respectively. Ji Huili study showed that among 22 patients with pulmonary embolism, 6 cases were misdiagnosed as pneumonia, 5 cases of acute coronary syndrome, 5 cases of heart failure, 2 cases of acute attack of chronic obstructive pulmonary disease, 2 cases of cerebrovascular accident, 1 case of infectious shock, and 1 case of pleurisy. The misdiagnosis time ranged from 1 to 7 d, with an average of 3.2 d. It can be seen that the most common misdiagnosis of pulmonary embolism is pneumonia, tuberculosis and left heart failure, because pulmonary embolism is commonly shown as patchy shadow, pleural effusion, and solid lung shadow on X-ray, which is easy to misdiagnose pneumonia and tuberculosis; because patients often have sudden whistling difficulty and cough, if it cannot be explained by lung inflammation. It is also easy to consider acute left ventricular failure, and the main reason for misdiagnosis is the lack of awareness of pulmonary embolism. Due to the lack of awareness, lack of relevant basic examinations, lack of obvious clinical symptoms and signs in some patients, no obvious abnormalities on chest X-ray and delayed appearance of imaging are also the reasons for misdiagnosis. Early diagnosis and timely treatment of pulmonary embolism can significantly reduce the mortality rate, and the Stern study found that the mortality rate decreased significantly to 2%-8% after clear diagnosis and adequate treatment. However, there is a high rate of misdiagnosis in clinical practice, and in China, there is little epidemiological data on pulmonary embolism and a lack of awareness of the disease. Therefore, physicians at all levels, especially front-line clinicians, should increase their awareness of pulmonary embolism.