The diagnosis of lung cancer consists of three parts: the first is imaging diagnosis, the most common one is chest CT scan; some patients have examined chest X-ray and found lung shadows, and then underwent chest CT examination. The main role of imaging examination is two, one is to detect the primary lesion and the second is staging. If the lesion is limited, local treatment including surgery and radiation therapy can be performed; if the lesion is extensive, the treatment is mainly systemic. Is imaging alone sufficient to diagnose lung cancer? No. Therefore, the second part of lung cancer diagnosis is the most important, which is cytology or pathology. Cytologic and pathologic diagnosis includes sputum examination, bronchoscopic cytology and pathology, lung puncture biopsy, mediastinoscopy, and open chest biopsy if necessary. The treatment of lung cancer is mainly based on histological types, including EGFR mutation detection, which has been widely used in clinical practice. The third part is the assessment of organ function.