Cough for three months has been bad may be chronic bronchitis, bronchiectasis, tuberculosis, lung tumors and other reasons. 1. Chronic bronchitis: chronic non-specific inflammation of the bronchial mucosa and its surrounding tissues is the main feature of chronic bronchitis, bacterial, viral, mycoplasma and other infections, is a common factor in the development of the disease, the patient’s annual onset of the disease will continue for more than three months, and continue for two years or more. Smoking, air pollution is also a predisposing factor. 2. Bronchial dilatation: after repeated occurrence of bronchial inflammation, the patient’s bronchial wall destruction, airway gradual expansion, distortion, wall damage is generally irreversible, the course of the disease is usually longer, there has been coughing for three months or even may be longer. 3. Tuberculosis: when the patient’s resistance is low, tuberculosis bacillus may multiply in the lungs and cause inflammatory reaction, which stimulates the airways and produces coughing, and the patient may keep coughing for three months, and may have symptoms such as low fever in the afternoon and hemoptysis. 4. Lung cancer: Bronchial cavity tumor or peribronchial lung parenchyma tumor constantly stimulates and presses the bronchial tube, which usually causes coughing symptom, and it may be manifested as coughing for three months or longer. If your cough has been bad for three months, you need to consult a regular hospital in time, and cooperate with the doctor to improve the examination and standardize the treatment.