Tumor markers are substances synthesized and released by tumor cells themselves, or produced or elevated by the body in response to tumor cells. Tumor markers exist in blood, cells, tissue fluids and body fluids, and respond to the existence and growth of tumors, and can be detected through chemical, immunological and genomic examination methods. Tumor markers can be used to diagnose tumor diseases and to make a clear judgment on the efficacy of tumor diseases, whether they recur or not, and the prognosis of tumor diseases, which is a commonly used clinical test. Commonly used tumor markers include alpha-fetoprotein test, which has very important reference value for the diagnosis of liver cancer, carcinoembryonic antigen test for the diagnosis of digestive tumors, and prostate-specific antigen for the diagnosis of prostate cancer.