Tumor marker testing has a role in screening for tumors. Because tumor markers are substances that can be detected in the blood and are often related to tumors, sometimes they may be earlier than imaging findings, so they have a certain role in early screening of tumors. Moreover, some tumor markers have a certain role in the screening of cancer, for example, AFP often suggests the need to pay attention to liver tumors. Tumor markers are substances released into the blood by tumor cells themselves or by the body stimulated by diseases, often elevated in neoplastic diseases, and sometimes found earlier than ultrasound, CT, MRI and other imaging tests, so they have a certain role in the early screening of tumors. Some tumor markers have a certain suggestive effect on cancer screening, such as AFP is often elevated in liver cancer, which should pay special attention to the liver; CA199 is often elevated in pancreatic cancer, which should pay special attention to the pancreas; CEA is often elevated in gastrointestinal tumors, which should pay special attention to the gastrointestinal tract and so on. Therefore, tumor markers have a certain role in screening of tumors, and patients can choose and test them under the recommendation and guidance of doctors.