A large number of data show that smoking has a certain relationship with chronic bronchitis. Smoking can make bronchial epithelial cilia shorter, irregular, ciliary movement disorders, reduce local resistance, weaken the phagocytosis and sterilization of alveolar phagocytes, and cause bronchospasm, increase airway resistance. Sulfur dioxide in chemical gases is closely related to the disease. In addition, the chemical poison in the atmosphere, dust and irritant smoke can also cause disease. 2., the internal factors are respiratory local defense, low immune function and autonomic nerve dysfunction. Especially in the elderly, respiratory tract tissue degeneration and immune dysfunction are more susceptible to pathogenic microorganism infection. 3. infection factors: respiratory tract infection is another important factor for the onset and exacerbation of chronic bronchitis. According to the research of our country in recent years. The most common bacteria in the phlegm of the patient are Streptococcus green, Neisseria, Diplococcus pneumoniae and Haemophilus influenzae, four species. In particular, the latter two are considered to be the most important pathogenic bacteria of the disease. Virus infection also has a great relationship with the attack of the disease. In the period of isolation of the virus of chronic bronchitis acute attack with rhinovirus, influenza virus, respiratory syncytial virus, adenovirus and mycoplasma is the main pathogen of the disease caused by cold and excited. The injury of the respiratory epithelium caused by virus infection is beneficial to the secondary infection of bacteria and causes the occurrence and repeated attacks of the disease. 4., allergic factors: after preliminary observation of sensitive factors, such as metabolites of bacterial infection, some inhalation substances (mold spores, insecticides, chemical gases, etc.), air temperature and air pressure are the causes of rapid and delayed allergic reactions of chronic bronchitis. Chronic bronchitis, especially asthma, sputum eosinophil numbers are generally higher; some other rheumatoid factor in the serum of patients with higher than normal group, and found that the increase of IgG content in lung tissue of severe chronic bronchitis, also have a certain relationship with that type III hypersensitivity. Most of the patients are prone to onset in the cold season, especially in the elderly. Cold air can cause the secretion of mucus to increase, and the bronchial ciliated movement is weakened. Anaphylaxis and dysregulation of respiratory function are also important reasons.