Lung cancer is easily misdiagnosed in its early stage. Its symptoms mainly include cough, blood in sputum, fever and chest pain, which can easily be regarded as “lung inflammation” or “pulmonary tuberculosis”, especially for those patients with a history of bronchitis or bronchial dilatation and a history of coughing and hemoptysis in their daily life. It is more likely to be overlooked, resulting in delayed diagnosis and treatment. Lung cancer is more common in men around 45 years of age who smoke more than 20 cigarettes a day. In this group, if symptoms such as irritating dry cough and blood in sputum occur, patients should seek medical attention as early as possible and follow the physician’s instructions for necessary tests, such as chest X-ray, sputum for cancer cells, fiberoptic bronchoscopy, chest CT and percutaneous lung puncture. In addition, blood tests can also be done. Sometimes, it is not possible to find out the cancer cells at one time, so it is necessary to check repeatedly until it is clear. Regular chest X-ray every 6 months, CT examination if necessary and sputum to find cancer cells are the main methods to detect asymptomatic lung cancer and are worth advocating. In addition, for some people with extra-pulmonary symptoms and signs, such as pestle and toe, gynecomastia, sudden skin disease and other manifestations, further examination should also be done to prevent early lung cancer from being missed.