CEA stands for carcinoembryonic antigen and is a marker for gastrointestinal tumors. If it is significantly increased, further investigations should be performed, except for malignant tumors of the gastrointestinal tract, which usually require abdominal CT as well as fiberoptic colonoscopy and gastroscopy. For malignant tumors occurring in the stomach and large intestine, the determination of carcinoembryonic antigen will be significantly increased. After the diagnosis is clear, radical resection surgery should be performed in a timely manner, usually by traditional open surgery or laparoscopic surgery, and postoperative symptomatic treatment such as infection prevention and nutritional support should be given. After the surgery, the detailed pathological staging and immunohistochemistry results should be taken into account to choose the adjuvant treatment plan. Many patients need to undergo systemic intravenous chemotherapy after the surgery, and regular postoperative colonoscopy should be performed, mainly to prevent recurrence and metastasis.