Cough is a common symptom of respiratory diseases and many diseases can cause cough. The most common causes of persistent cough: first, cough variant asthma. Cough variant asthma is most often seen in special constitutions where certain allergic factors to the external environment exist, causing cough-based bronchial asthma, and such patients should be treated as bronchial asthma in terms of treatment. Second, lung tumor. Patients with lung tumors can cause persistent coughing, and it can be accompanied by weight loss, lethargy, coughing, coughing up blood and other symptoms. Third, gastroesophageal reflux. Gastroesophageal reflux can also cause a persistent cough and requires attention to exclusion. In conclusion, persistent cough can be caused by so many diseases and further tests, such as chest CT, bronchoscopy, pulmonary function and other tests, are needed for further clarification.