Alpha-fetoprotein (AFP) is a glycoprotein synthesized by the liver during early fetal life, and its synthesis is soon suppressed after birth. The gene is reactivated when malignant lesions occur in stem cells or germline embryonic tissue, causing cells that had lost the ability to synthesize AFP to start synthesizing it again, resulting in a significant increase in blood AFP levels. Therefore, the blood AFP concentration test is of great clinical value in the diagnosis of cell carcinoma and trophoblastic malignancy. Clinical significance: 1. The value of increased serum AFP in primary hepatocellular carcinoma patients is more certain in the diagnosis, judgment of efficacy, prognosis detection and recurrence of hepatocellular carcinoma, with a sensitivity of 65-70%. 2.In germline embryonal cancer (testicular cancer, ovarian cancer, teratoma, etc.) gastric cancer, or pancreatic cancer, AFP is increased. 3.AFP is increased to varying degrees in viral hepatitis and liver cirrhosis. 4.AFP increases during pregnancy, reaching a peak in July~August and decreasing later.