Bronchial asthma and slow-onset lung can be differentiated according to age, clinical symptoms, and various examinations. 1, the difference of age of onset: slow obstructive pulmonary mostly develops after middle age, while asthma mostly develops in childhood or adolescence. 2, the difference of the onset of background: slow obstructive pulmonary more long-term history of smoking, breathing harmful gases, particles exposure history, asthma is the patient is allergic, such as: allergic rhinitis and (or) eczema, etc., some patients have a family history of asthma. 3, the difference between the characteristics of airflow restriction: bronchial asthma is a reversible airway obstructive disease, and slow obstructive lung is an irreversible airway obstructive disease. However, for middle-aged and elderly patients, it is sometimes difficult to distinguish between the two, and some patients can be diagnosed as asthma combined with slow-onset lung or slow-onset lung combined with asthma, so the differentiation of the two needs to be done by professional respiratory doctors.