Has been coughing for 3 months has not improved, this time should be a clear diagnosis, timely symptomatic and etiological treatment, you can test the blood routine, lung function, exhaled nitric oxide, take lung CT, do PPD test, if necessary, can also take sputum, do the culture of pathogens. If it is clear that the tuberculosis is caused by Mycobacterium tuberculosis infection, a combination of anti-tuberculosis drugs can be given, such as rifampicin, isoniazid, ethambutol, pyrazinamide and other drugs can be chosen. If it is clear that there are occupying lesions in the lungs, the occupying lesions in the lungs can be taken at this time and biopsy can be done to clarify. If it is lung cancer, it should be treated with surgery as early as possible and given a combination of radiotherapy and chemotherapy.