Bronchoscopy is a necessary examination item for patients with lung tumor, which mainly has the following purposes: 1. To clarify the diagnosis and determine the benignity and malignancy. Patients with lung cancer mostly present as lung masses, and most of them can make preliminary diagnosis through CT and other imaging examinations, but they are only imaging diagnoses. Although in most cases, the diagnosis of high-level radiologists is consistent with future pathological diagnosis, it can never be the gold standard for confirming the diagnosis. In order to get a cytological or pathological diagnosis, bronchial examination should be routinely performed, and microscopic brushing or tissue biopsy can be performed to achieve a true diagnosis, so that effective treatment can be given according to the pathological diagnosis. Some lung cancers often infiltrate along the bronchial wall, so bronchoscopy is needed to visually understand the real extent of lesion invasion, so as to make an exact judgment for the scope of surgical resection and avoid excessive or insufficient resection. 3.Effective treatment Some patients with lung cancer have been clearly diagnosed through sputum cytology, but they also need bronchoscopy, which can provide effective treatment, such as washing the sputum in the bronchial lumen and removing the detached tumor in the lumen, all of which can lay a good foundation for surgery or provide better conditions for other treatments. 4.Pay attention to multiple sputum cytology examination Not all patients can get cellular or pathological results after bronchoscopy brush and biopsy, because tumor is not growing on the surface, after the so-called slight damage of bronchus, it can make relatively deep tumor exposed and tumor cells can be shed more easily, therefore, sputum should be routinely kept for cytology examination on the day after bronchoscopy, the positive rate is higher.