In recent years, pulmonary function test has received more and more clinical attention; it is a routine test in respiratory medicine, and it has become an indispensable test in other departments such as anesthesiology, before surgery, occupational disease identification, etc. It plays a very important role in the diagnosis and differential diagnosis of many diseases, and pulmonary function test is an important basis for the diagnosis of chronic obstructive pulmonary disease, severity grading, condition monitoring and drug treatment effect evaluation. Patients with atypical bronchial asthma often show chest tightness, breathlessness and chronic cough, which are often misdiagnosed as heart disease or lung infection and delay the diagnosis and treatment.