AFP is the most important blood tumor marker for primary liver cancer. serum AFP concentrations in infants from 3 months to a week old are approaching adult levels. In general, serum concentration in healthy adults is less than 25μg/L. Detection of AFP and imaging tests such as ultrasound can help in the early diagnosis of liver cancer, and even detect microscopic or small liver cancer without symptoms or signs. The diagnosis of hepatocellular carcinoma can be considered when serum AFP is ≥ 400 μg/L, persistently elevated and pregnancy, active liver disease and germinal gland embryonic-derived tumor can be excluded. In patients with primary hepatocellular carcinoma, a large amount of alpha-fetoprotein exists in the serum, and it can be detected 8 months before the appearance of clinical symptoms, when most patients with hepatocellular carcinoma still have no obvious symptoms and small tumors. Therefore, patients with cirrhosis, chronic hepatitis and those who have liver cancer in their family should be tested every six months. Most patients with hepatocellular carcinoma have continuously elevated serum alpha-fetoprotein levels, but some patients have low elevated levels, i.e. 20-400 μg/L. However, 18-20% of patients with primary hepatocellular carcinoma have normal serum alpha-fetoprotein. After hepatocellular carcinoma surgery, the value of alpha-fetoprotein gradually decreases; if the decrease is not significant, it indicates incomplete surgery or recurrence. The measurement of alpha-fetoprotein has important clinical significance for the diagnosis of primary liver cancer and the follow-up of treatment.