Most patients with pulmonary embolism first consult the primary hospital. In the primary hospital, due to the limitation of medical conditions, in order to avoid misdiagnosis and underdiagnosis of pulmonary embolism, when the first physician receives a patient with clinical manifestations such as chest tightness and breathlessness, palpitation, chest pain, shortness of breath during activity, frequent syncope or with right heart insufficiency, he/she should ask detailed medical history, such as whether there is deep vein thrombosis of lower limbs, tumor, chronic heart disease, oral History of contraceptive drugs, careful physical examination. Most of the primary hospitals, although they cannot perform pulmonary arteriography, nuclear lung ventilation/perfusion scan, but they can perform laboratory, electrocardiogram, echocardiogram and chest X-ray and other routine auxiliary examinations, and advocate to carry out plasma D-dimer testing, which will bring insight to the diagnosis. The multiple clinical and ancillary examination manifestations of pulmonary embolism can dazzle and confuse clinicians in recognizing pulmonary embolism. In order to help primary care physicians improve their clinical skills in the diagnosis and management of pulmonary embolism, this section discusses the “original” pulmonary embolism. Key point: close combination of clinical manifestations and auxiliary examinations Patients with pulmonary embolism have various manifestations, but the specificity for diagnosing pulmonary embolism is not high. Therefore, the diagnosis of pulmonary embolism at the primary level should establish a comprehensive data analysis system and diagnostic process, pay attention to differential diagnosis, and make a comprehensive clinical diagnosis by integrating the meaningful results of various auxiliary examinations, clinical manifestations and risk factors. For example, for patients with chest pain, is an inverted T wave in the chest lead of ECG necessarily coronary artery disease? Attention needs to be paid to the differentiation. If the patient detects significantly elevated blood D-Dimer, CK-MB is not high, accompanied by ECG SⅠQⅢTⅢ and pulmonary hypertension on cardiac echocardiography, it suggests a high possibility of pulmonary embolism. The results of the meta-analysis of domestic literature done by the author suggest that laboratory, electrocardiogram, echocardiogram and chest X-ray can be used as routine tests for screening pulmonary embolism, which has some guiding significance for the initial diagnosis of pulmonary embolism, especially more important for primary hospitals. The Wells score, modified Geneva score and Dutch study scale can be used to clinically assess the likelihood of pulmonary embolism and to make appropriate judgments about the risk stratification of acute pulmonary embolism for treatment purposes. Only by avoiding underdiagnosis, misdiagnosis and “overdiagnosis” can pulmonary embolism be “revealed”. In order to avoid blind diagnosis, further standardization should be carried out. It should be emphasized that there are many classifications of pulmonary hypertension diseases, and pulmonary hypertension is a kind of pathophysiological syndrome caused by the progressive increase of pulmonary circulatory resistance due to the involvement of pulmonary vascular bed by various etiologies, which eventually leads to right heart failure. It can be divided into 5 types, and pulmonary embolism belongs to category 4: chronic thrombotic and/or embolic pulmonary hypertension, and attention should be paid to screening and diagnosis. It is important to avoid both underdiagnosis and misdiagnosis, as well as overdiagnosis, and must be handled carefully. Currently, the situation of “overdiagnosis” of pulmonary embolism is also “growing quietly”. For example, we encountered a patient who was transferred from a primary hospital after trauma, with chest tightness, hypoxia, rapid heart rate, high D-Dimer, lung shadow, and right ventricular overload on ECG and echocardiogram, and was diagnosed as pulmonary embolism, but further examination revealed that intestinal perforation led to respiratory distress syndrome (ARDS); we also encountered a patient with SⅠQⅢTⅢ on ECG, swelling of both lower extremities, and jugular vein angina. The first diagnosis was pulmonary embolism, which resulted in a diagnosis of idiopathic pulmonary hypertension in a higher level hospital. The author also encountered a patient who was initially misdiagnosed as pulmonary embolism and finally diagnosed as familial pulmonary hypertension, which was published in the form of a teaching seminar in Chinese Community Physician, 2014, 17. Therefore, the patient should be diagnosed as “suspected”, “probable” and “definite”. The reference process for the diagnosis of pulmonary embolism in primary care hospitals is shown in Figure 1. Figure 1 Reference process for the diagnosis of pulmonary embolism in primary care hospitals