The treatment effect of lung cancer is closely related to the early diagnosis of lung cancer. Therefore, early diagnosis and early treatment should be strongly advocated to improve survival rate or even cure rate. This requires clinicians with high vigilance, detailed medical history, experience in symptoms, signs and imaging of lung cancer, and timely cytological and fibrinoscopic examinations, which can confirm the diagnosis of 80% to 90% of lung cancer patients. The early diagnosis of lung cancer depends on the efforts of many aspects. ①Popularize the knowledge of lung cancer prevention and treatment, so that patients with any suspicious symptoms of lung cancer can seek medical consultation in time, and long-term heavy smokers over 40 years old or those with a history of exposure to risk factors should have annual medical checkups for cancer prevention or lung cancer exclusion tests. ② Medical personnel should be alert to the early signs of lung cancer to avoid missed diagnosis and misdiagnosis. People with high-risk factors or those with the following suspicious signs should be screened: irritating cough lasting 2-3 weeks with no obvious cause and ineffective treatment; chronic respiratory disease with a change in the nature of cough; persistent or repeated blood in sputum or hemoptysis within a short period of time with no other explanation; repeated episodes of pneumonia in the same area, especially non-segmental pneumonia; unexplained joint pain in the extremities and pestle-like fingers (toes). imaging suggestive of limited emphysema or segmental or lobar atelectasis; isolated round lesions and unilateral increased hilar shadowing; original tuberculosis lesions that have stabilized and have changed in form or nature; pleural effusion without toxic symptoms, especially if it is hemorrhagic and progressively increasing. With one of the above manifestations, it is worthy of suspicion and requires necessary auxiliary examinations, including imaging, especially low-dose CT scan is a valuable method for census detection of lung cancer at present. ③ Development of new early diagnostic methods, such as markers for early diagnosis, but cytology and pathology examination are still necessary to confirm the diagnosis of lung cancer. Early diagnosis of lung cancer definitely determines its prognosis. A former teacher whom I respect very much found a small nodule in the lung two years ago and dynamically observed it for two years before it grew 0.3cm recently and immediately operated and diagnosed as lung cancer, which is really a pity! If early surgery is possible, the prognosis is much better!