Lung cancer is often at an advanced stage when symptoms are detected. Early detection and early treatment are the keys to improve the prognosis. Early symptoms of lung cancer are hidden, especially peripheral type adenocarcinoma, which will be diagnosed early only by regular examination. When the symptoms of adenocarcinoma are obvious, pleural fluid or bone metastasis and brain metastasis often occur. The one-sided understanding of lung cancer development and having paralysis are the reasons for delayed diagnosis. Some patients think that they will not get lung cancer if they do not smoke. Smoking is indeed the main cause of lung cancer, but it is not the only cause. Long-term inhalation of secondhand smoke is also a cause of lung cancer. In addition, cooking fumes and environmental air pollution are also causative factors. Lung cancer is also associated with family history. Another misconception is that many people believe too much in routine medical checkups and do not undergo specialized lung cancer examination. In fact, conventional X-ray chest films are not sensitive enough to detect small lesions or lesions hidden behind the heart. The CT chest examination applied for lung cancer screening is highly accurate and can detect early stage IA lung cancer with diameter less than 0.3 cm, and the five-year survival rate can reach more than 90% if radical treatment is given at this time. Therefore, it is recommended that people with high risk of lung cancer (middle-aged and elderly people; urban men who have smoked more than 400 cigarettes for years; people with long-term exposure to occupational factors that are likely to cause lung cancer; people working in long-term air pollution environment; people with family history of lung cancer or other malignant tumors; and people with chronic respiratory diseases) should have annual low-dose spiral CT examination of the chest, and if small masses are found, they should be dynamically reviewed every three to six months. When the relevant high-risk group develops persistent irritating cough, sputum with blood, etc., they should undergo specialist lung examination. The purpose of lung cancer screening is to detect early lung cancer in preclinical stage and to remove it surgically in an attempt to cure it. Findings show that early stage lung cancer may survive for a long time after timely surgery. Undetected patients, on the other hand, develop cancer metastasis within six to seven years.