The key to treat tumors is early detection, early diagnosis and early treatment. Most patients have already lost the best time for treatment when they are diagnosed. Tumor marker testing is widely used in the diagnosis and efficacy assessment of tumors, and has become one of the methods for early detection of tumors. Tumor markers are substances synthesized and released by tumor cells or released by the host in response to tumor during the development of tumor, which have important clinical value in early diagnosis, disease monitoring and prognosis of tumor. The ideal tumor markers should have high sensitivity, good specificity, organ specificity, good correlation with the severity of disease, tumor size or stage, and be able to evaluate the therapeutic effect and predict the prognosis of tumors. However, single tumor marker test is still difficult to meet the above requirements, so it is important to select related tumor markers for combined test. The sensitivity of CEA for primary screening of GI tumors is generally 50%-70%. Serum CA199 is considered a tumor-associated antigen with high specificity for GI tumors, with a positive detection rate of 47.06% and specificity of 83.3% in benign diseases, which is lower than CEA and CA242, suggesting that the specificity of CA199 is not high. In contrast, the expression of CA242 antigenic determinants in malignant tumors is more specific, and in terms of specificity and accuracy, CA242 is higher than CEA and CA199, especially in colorectal and pancreatic cancers. It has been reported that the detection rate of CA242 is significantly higher in the GI tumor group than in the benign disease group (P<0. 01), and it can be considered that ca242 has independent value in the differentiation of benign and malignant GI diseases. However, tumor markers are not only produced in the case of cancerous lesions, but also sometimes occur in the case of some normal tissues and benign lesions. In recent years, domestic and foreign scholars have advocated the use of combined, dynamic surveillance to improve tumor detection rates. Since there is only a certain correlation between the indicators themselves and the tumor condition, and there are more influencing factors affecting these indicators, the accuracy and precision of the tumor indicators are lacking to some extent. A few patients with high rise of tumor indicators are finally diagnosed as not malignant tumors. As for the accuracy of a certain index indicating the origin of tumor is relative, not absolutely reliable. For example, elevated CA199 only indicates that pancreatic and digestive tract tumors are more likely, but tumors in other areas are also possible. In addition, the degree of elevation of the index and the severity of the tumor disease are not proportional to each other. For this reason, several tumor indicators are often tested at the same time in order to improve their accuracy and precision in clinical practice. So how to judge the significance of elevated tumor indicators? What should be done when tumor indicators are high? Generally speaking, a slight increase in a single index (<50%) can be reviewed regularly and observed closely; if several indexes increase several times, a comprehensive examination such as CT and ultrasound should be conducted. It is advisable to seek consultation from oncologists (not other specialists) to determine the significance of elevated tumor indicators and their countermeasures.