Chronic hepatitis and cirrhosis are 100-200 times more likely to develop liver cancer than others. Methemoglobin is currently one of the most specific and sensitive serological tests for the diagnosis of liver cancer. In patients with hepatocellular carcinoma, about 50% – 80% of serum fetoprotein levels are above 300 μg/L, which is one of the early diagnostic indicators of primary hepatocellular carcinoma. Regular rechecking of fetoprotein in patients with chronic hepatitis and cirrhosis can assist in early detection of liver cancer for timely treatment. The rise and fall of alpha-fetoprotein can be used as an indicator to judge the prognosis of liver cancer or to observe the effect of surgery and various anti-cancer treatments: after surgical resection or various treatment measures are taken after the diagnosis of liver cancer, a significant decrease of alpha-fetoprotein indicates that the treatment is effective; if it increases again after the decrease, it indicates that liver cancer has signs of recurrence and metastasis. In some benign liver diseases such as acute hepatitis, chronic hepatitis and cirrhosis, when liver inflammation is active, hepatocytes are in the process of damage, repair and regeneration, and alpha-fetoprotein will rise, but the concentration is usually not too high, mostly below 200μg/L. As hepatitis improves, alpha-fetoprotein will drop and gradually return to normal. It is a good indicator for monitoring hepatocellular carcinoma, especially for early diagnosis of small hepatocellular carcinoma, but clinical practice is complex and varied. It is inappropriate to make a diagnosis of hepatocellular carcinoma on the basis of elevated alpha-fetoprotein alone. A correct diagnosis can only be made after a comprehensive analysis of medical history, symptoms, and various laboratory and imaging data.