This kit is used for quantitative detection of carbohydrate antigen 242 (CA242) in human serum in vitro. CA242 is a sialylated carbohydrate antigen, which can be recognized by CA242 monoclonal antibody. It is a kind of glycoprotein of mucin type, which is very low in the serum of healthy people and patients with benign diseases. When malignant tumors occur in the digestive tract, the serum CA242 usually increases. For example, with 17u / ml as the positive value, 86.2% and 62% of pancreatic cancer, colorectal cancer and rectal cancer were detected, respectively. The false positive rate of normal people was 4%. The reagent is mainly used for the diagnosis and detection of pancreatic cancer, colorectal cancer and rectal cancer. It also has a certain positive detection rate for lung cancer, breast cancer, etc.