Lung function is a commonly used test in respiratory medicine, and several common indexes that can be seen in the lung function report card have corresponding clinical significance, for example, exertion lung volume is used to replace the standard of lung volume, to clarify the maximum pulmonary ventilation, the end-expiratory volume at the end of the first second of exertion is used to determine the degree of impaired pulmonary ventilation, the rate of the first second of exertion expiratory volume, and the ratio of the first-second exertion volume, and the exertion lung volume or lung volume, mainly used to distinguish clinical obstructive and restrictive and mixed ventilation dysfunction, and also includes pulmonary carbon monoxide diffusion volume. The one-second rate is the ratio of the first-second expiratory volume to the expiratory lung volume or spirometry, which is used to differentiate between clinically obstructive, restrictive, and mixed ventilatory dysfunction, and to assess the severity of the disease based on the corresponding values, and the pulmonary carbon monoxide diffusion volume, which is the main indicator of diffusion function. In addition, two other commonly used tests include the bronchial provocation test, where a decrease in expiratory volume of more than 20% in the first second of exertion is judged to be positive. Bronchodilator test, after the use of drugs, the first second expiratory volume of force, more than 12% than before the use of drugs, and its absolute value increased by 200 ml is considered positive, both tests are helpful in the diagnosis and differential diagnosis of asthma.