CA199 and carcinoembryonic antigen may be elevated in patients with gastric cancer, while some patients have normal levels. CA199 is a glycan antigen, which is expressed in patients with many types of cancers, such as pancreatic, gastric, colorectal, and cholangiocarcinoma, etc. Its positivity rate is about 40% in patients with gastric cancer, and it can only be used as a screening for gastric cancer. The positive rate of CA199 in patients with gastric cancer is about 40%. CA199 can only be used as an indicator for gastric cancer screening, prognosis and evaluation of treatment effect, and has limited diagnostic value for gastric cancer. Carcinoembryonic antigen is a broad-spectrum tumor marker, which can be elevated in patients with gastric cancer, pancreatic cancer, colon cancer, and bile duct cancer, but its organ-specificity is relatively poor, and its elevated level can only be found in some patients with gastric cancer, therefore, whether the level of carcinoembryonic antigen is elevated or not can not diagnose or exclude the possibility of gastric cancer completely. Tumor marker level is not necessarily related to the presence or absence of cancer, and normal level cannot completely exclude the possibility of cancer, which needs to be considered in combination with endoscopy, imaging examination and pathological examination. Patients who are suspected of having gastric cancer are recommended to go to the hospital as soon as possible and undergo gastroscopy combined with histopathological biopsy to make a clear diagnosis.