There are several gastrointestinal tumor markers, such as CA199, CEA, CA50 and so on. When gastrointestinal tumors are suspected, it is necessary to draw blood for tumor markers to make a judgment. If the stomach and intestines are malignant tumors, the tumor markers will be significantly elevated. 1. CA199: it is a kind of glycan antigen, the elevation suggests that there may be malignant tumors of the digestive tract, such as pancreatic cancer, gastric cancer, colorectal cancer, etc., and there may be malignant diseases of the liver and gallbladder, such as cholecystolithiasis, cholangiocarcinoma, etc. 2. CEA: carcinoembryonic antigen, a broad-spectrum tumor marker, can help diagnose malignant tumors of the digestive system, such as colorectal cancer, pancreatic cancer, gastric cancer and so on. 3. CA50: belongs to salivary acid ester and salivary acid glycoprotein, which does not exist in normal human body, its elevation suggests pancreatic cancer, with a relatively high positive rate, and also suggests colon cancer, rectal cancer, gastric cancer and so on. Tumor markers can also be used for postoperative review of gastrointestinal tumors. Elevated tumor markers need to be further examined through abdominal CT, gastroscopy and other tests to clearly diagnose the presence of gastrointestinal tumors.