Since the incidence and mortality of pulmonary thromboembolism (PTE) are quite high, early diagnosis and treatment become the key to improve the prognosis. However, the diversity and lack of specificity in its clinical manifestations lead to serious misdiagnosis and missed diagnosis. This article sums up and sorts out the occurrence and causes of delayed diagnosis of PTE based on 3 levels, patients, clinicians and hospitals, and focuses on the differential thinking between PTE and confusing diseases (coronary heart disease, pneumonia, chronic obstructive pulmonary disease) in order to improve the early diagnosis rate of PTE.