Carcinoembryonic antigen (CEA), originally found in colon cancer and fetal intestinal tissue, is a broad-spectrum tumor marker. It is mainly used to determine the efficacy, disease progression, monitoring and prognosis estimation of colorectal cancer, pancreatic cancer and lung cancer. However, its specificity is not strong, its sensitivity is not high, and its role in early diagnosis of tumors is not obvious. Elevated CEA is commonly found in colorectal cancer, pancreatic cancer, gastric cancer, small cell lung cancer, breast cancer, and medullary thyroid cancer. However, smoking, pregnancy and cardiovascular diseases, diabetes mellitus, non-specific colitis and other diseases, serum CEA will also be elevated in 15% to 53% of patients, so CEA is not a specific marker for malignant tumors and has only auxiliary value in diagnosis. In addition, there is a clear relationship between serum CEA level and the stage of colorectal cancer, the more advanced the lesion, the higher the CEA concentration. The reference value of CEA is: <5.0ng/ml. when CEA>20ng/ml, tumor is highly suspected; when CEA>60ng/ml, it is seen in colon cancer, rectal cancer, gastric cancer and lung cancer. Generally speaking, CEA level will return to normal 6 weeks after surgical resection, otherwise it indicates residual tumor. For example, some benign inflammation, polyps and smoking and drinking can cause a mild increase in CEA. If CEA is found to be increased in physical examination, on the one hand, regular checkups of stool routine, colonoscopy, gastroscopy, chest X-ray, etc., on the other hand, we should pay attention to diet and change some bad habits. The diagnosis of tumor needs to be considered comprehensively. The following strategies can be adopted when high CEA is found in physical examination: 1. Go to hospital for a comprehensive further cancer prevention physical examination. 2. 2.Follow the doctor’s advice and monitor the CEA dynamically for a period of time. 3. Get a detailed physical examination and comprehensive analysis of laboratory results from an oncologist.