How long it is suitable to do PET-CT after gastric cancer surgery depends on whether the patient shows signs of suspected systemic metastasis, and it is suitable for those with high suspicion and vice versa. PET-CT, also known as positron emission computed tomography, is a kind of examination that combines both metabolism of lesions and precise localization by imaging. PET-CT has obvious advantages over traditional imaging methods, as it can show the abnormal metabolism of the tumor site at an early stage and locate it accurately by injecting the contrast agent intravenously. Currently, PET-CT is used in postoperative cancer patients mainly for early detection of possible metastatic foci when there is a high suspicion of systemic metastasis.