Small airway lesions are lesions in airways with a diameter of less than two millimeters. Small airway lesions are common in diseases such as chronic obstructive pulmonary disease (COPD), bronchiectasis, and bronchial asthma. Chronic Obstructive Pulmonary Disease (COPD) is most common in middle-aged and elderly people who have been smoking for a long time, and is mainly characterized by dyspnea after activity, accompanied by coughing and sputum. Bronchiectasis is characterized by recurrent coughing, coughing up purulent sputum, sometimes accompanied by hemoptysis and dyspnea. Chest CT can clarify the diagnosis. Bronchial asthma is most common in children and adolescents, mainly manifested by recurrent cough, chest tightness, wheezing and other symptoms, bronchial provocation test can assist in the diagnosis. After the appearance of symptoms related to small airway pathology should be timely to the hospital, standardized treatment, in order to avoid delay.