With the increase of industrialization and the deterioration of environment, the incidence and mortality rate of lung cancer are increasing year by year in today’s society. Currently, lung cancer ranks first among malignant tumors in terms of incidence and mortality. Early stage lung cancer lacks specific symptoms and is difficult to be detected. Since early stage lung cancer lesions are small and do not invade the surrounding organs heavily, and no distant metastasis has occurred, radical resection is possible and the prognosis is better. Most of the lung cancers seen in clinical practice are in advanced stages, and most cases are inoperable when detected. Among the lung cancer patients, most of the early stage lung cancers are detected by physical examination or unintentionally, which is due to asymptomatic or atypical symptoms in early stage. Therefore, early detection and diagnosis play a key role in improving the survival rate of lung cancer. Currently, there are some methods for early detection of lung cancer as follows: 1. Chest X-ray: Chest X-ray is the preferred method for lung cancer screening and is more suitable for general population. With the development of imaging technology with higher sensitivity, chest X-ray is still located in the first line of lung cancer detection with low cost and easily accepted by patients. The sensitivity of chest radiography for lung cancer is about 80% and the specificity is 89% to 99%. However, it is often difficult to detect hidden lesions due to the obscuration of ribs, heart and other organs, which is its lacking aspect. 2.Sputum cytology examination: In early stage bronchial endoluminal lung cancer, cancer cells can be found in sputum when there is no suspicious lesion in X-ray chest film. This indicates that sputum cytology examination is earlier than X-ray detection. The positive rate of sputum examination is related to the correct method and frequency of sputum collection. Patients should be allowed to cough deeply, usually the first sputum after waking up in the morning is good. One negative test cannot negate the existence of lung cancer, and it is appropriate to send the test 4-6 times. It has been reported that the positive detection rate can reach 70%-80% after three consecutive tests. In recent years, some new diagnostic techniques have been applied to sputum cytology, such as checking the abnormal expression of genes and certain gene products, which can improve the positive rate of sputum cytology examination. Due to the poor compliance of some patients in sputum examination, the clinical application is less. 3.CT examination of chest: It can detect lesions in hidden parts of lung that cannot be detected by X-ray chest X-ray, and through images, morphological classification and image characterization of lesions can be made, and whether there is lymph node metastasis can be judged, so as to understand the progress of lung cancer. Chest CT has clear localization, high resolution, and can detect microscopic lesions in the lung at an early stage and take active treatment measures, which should be promoted in clinical work, especially for high-risk groups. 4.Fiber or electronic bronchoscopy: It is generally not used for early screening of lung cancer, but for high-risk groups, patients with positive chest CT, or those with moderate or severe atypical hyperplasia detected by sputum cytology and negative X-ray examination, bronchoscopy should be performed. 5.PET-CT imaging: Positron emission computed tomography (PET) is one of the most promising imaging techniques in current imaging technology, with high sensitivity, specificity and accuracy for single nodules in the lung. However, PET-CT examination is too expensive to be used routinely at present.