Chest X-ray examination of the lungs is normal, but also always dry cough is considered to be cough variant asthma, chronic pharyngitis, gastroesophageal reflux and other diseases. 1. Cough variant asthma: the cause of cough variant asthma is not clear, it is considered to be related to genetic, environmental changes and other factors, the patient will have an irritating dry cough, chest X-ray examination of the lungs is usually normal. 2. Chronic pharyngitis: chronic pharyngitis is mainly caused by repeated infections of viruses, bacteria and other pathogens. Patients will have dry throat, sore throat, dry cough and other manifestations. If chronic pharyngitis leads to dry cough, the patient’s lung function is also normal during chest X-ray examination. 3. Gastroesophageal reflux: Gastroesophageal reflux patients will manifest heartburn, chest pain, etc. If the reflux material stimulates the throat, dry cough will occur. At this time, patients undergo chest X-ray examination lung function is generally normal. Patients to do chest X-ray examination of the lungs normal but dry cough performance, can also be seen in other diseases, a number of cough serious need to consult a doctor in a timely manner to check, the doctor will be based on the cause of the disease to take targeted treatment.