Bronchoscopy can observe the situation of bronchial tubes in the lungs under direct vision, and it can also take biopsies for pathological examination, which is of great significance to the diagnosis of some lung diseases, such as central lung cancer, certain pulmonary tuberculosis, interstitial lung disease and so on. 1. Central lung cancer: bronchoscopy can clearly observe the growth or infiltration of the tumor in the bronchial tube, and can also take the tumor tissue under the microscope for pathological examination to clarify its pathological type, which can provide the basis for the next step of treatment, and it is one of the best examination modes to diagnose central lung cancer. However, due to the limitation of instruments, bronchoscopy cannot examine the peripheral lesions of lungs, and its significance to peripheral lung cancer is limited. 2. Certain pulmonary tuberculosis: bronchoscopy is mostly used for the diagnosis of bronchial tuberculosis, which can observe bronchial congestion, erosion, ulceration, scarring hyperplasia and so on, and it can also take the tissue of tracheal mucosa for the culture of tuberculosis bacillus. In addition bronchoscopy can also find lymph node bronchial fistula. 3. Interstitial lung disease: bronchoscopy can take lung tissue for pathologic examination, but also for bronchoalveolar lavage to further define the disease, for a variety of interstitial lung disease diagnosis has an important role, such as idiopathic pulmonary fibrosis, allergic pneumonitis, alveolar protein deposition disease, eosinophilic pneumonia, and so on. Although bronchoscopy is of high value in the diagnosis of many lung diseases, it also has certain limitations. It is recommended that patients go to the hospital as soon as possible, and consult with a medical professional to determine the appropriate test in light of their condition.