Lung cancer is one of the malignant tumors with the fastest growing incidence and mortality rates and poses the greatest threat to the health and lives of the population. In recent 50 years, many countries have reported a significant increase in the incidence and mortality of lung cancer, with men accounting for the first place in incidence and mortality of all malignant tumors, and women accounting for the second place in incidence and mortality. The etiology of lung cancer is not completely clear yet, but a lot of information shows that long-term heavy smoking has a very close relationship with the occurrence of lung cancer. 1.X-ray examination Through X-ray examination, the site and size of lung cancer can be understood, and local emphysema, pulmonary atelectasis or infiltrative lesions or inflammation in the lung adjacent to the lesion due to bronchial obstruction may be seen. 2.Bronchoscopy Through bronchoscopy, the lesions of bronchial lining and lumen can be directly observed. Tumor tissues can be taken for pathological examination or bronchial secretions can be aspirated for cytological examination to clarify the diagnosis and determine the histological type. 3.Cytological examination Sputum cytological examination is a simple and effective method for lung cancer screening and diagnosis, and most patients with primary lung cancer can find shed cancer cells in sputum. The positive rate of sputum cytology examination for central type lung cancer can reach 70% to 90%, while the positive rate of sputum examination for peripheral type lung cancer is only about 50%. 4.Thoracotomy If the nature of the lung mass is not clear after multiple examinations and short-term diagnostic treatment, and the possibility of lung cancer cannot be excluded, a thoracotomy should be performed. This can avoid delaying the disease and losing the opportunity of early treatment for lung cancer patients. 5.ECT examination ECT bone imaging can detect bone metastases at an early stage, and both X-ray and bone imaging have positive findings. It should be noted that the false-positive rate of ECT bone imaging for the diagnosis of bone metastasis of lung cancer can reach 20%-30%, so those who have positive ECT bone imaging need to have MRI scan of the positive area of bone. 6.Mediastinoscopy Mediastinoscopy is mainly used for patients with mediastinal lymph node metastasis, who are not suitable for surgical treatment and cannot be diagnosed pathologically by other methods. Mediastinoscopy should be performed under general anesthesia. A transverse incision is made in the superior sternal recess, the anterior soft tissues of the neck are bluntly separated to reach the anterior tracheal space, the anterior tracheal passage is bluntly freed, and a viewing scope is placed to slowly pass behind the innominate artery to observe the enlarged lymph nodes in the paratracheal, tracheobronchial angles and under the bulge.