Dry cough at night may be caused by centralized lung cancer, and it is also common in variant asthma or other diseases. 1. Centralized lung cancer: Early centralized lung cancer mass blocks the lumen of trachea, resulting in narrowing of airway, increased secretion in trachea and irritation of trachea, causing irritating dry cough. At night, parasympathetic excitability increases, airway sensitivity increases, and coughing is more than that in daytime. Long-term smokers with dry cough, ordinary cough suppressants can not be relieved, or with blood in sputum, should be alert to the possibility of lung cancer. 2. variant asthma: variant asthma airway hyperresponsiveness, clinical manifestations of more intense irritating dry cough, increased parasympathetic excitability at night when sleeping, increased airway sensitivity, night and early morning cough as its important features. 3. Other diseases: chronic pharyngitis, cardiac insufficiency, chronic reflux esophagitis and other diseases can also appear at night when sleeping dry cough. It is recommended to go to the hospital as soon as possible for further examination to clarify the diagnosis and exclude lung cancer.