PET-CT, or PET-CT, has an accuracy rate of more than 85% in detecting lung cancer, and plays an important role in both clinical diagnosis and pathologic staging evaluation of lung cancer. PET-CT is a non-invasive new imaging diagnostic technology, which makes up for the insufficiency of CT and PET alone through the complementarity of imaging information. PET-CT is one of the most advanced imaging devices to interpret lung lesions through both anatomical and functional aspects, and the active glucose metabolism of the lesion is reflected by the SUVmax value by measuring the 18F-FDG uptake value in PET-CT detection. Its application in the diagnosis of lung cancer has greatly improved the diagnostic effect, with an accuracy rate of more than 85%. PET-CT also has the possibility of false-positive and false-negative, so it should also be combined with tumor markers, pathological biopsy and other examinations for comprehensive diagnosis, of which pathological diagnosis is the gold standard. If lung cancer is detected by PET-CT, it is recommended to consult a doctor in time to further clarify the pathological diagnosis, so as to prevent misdiagnosis and omission of diagnosis, which may lead to adverse consequences.