Methemoglobin is a specific indicator for the clinical diagnosis of primary liver cancer. methemoglobin is a glycoprotein that exists mainly in liver cells during the embryonic period and disappears rapidly from the blood two weeks after the birth of a fetus, so that the amount of methemoglobin in the blood of a normal person is less than 20. when liver cells become cancerous, however, the function of producing this protein is restored, and with the rapid deterioration of the disease Methemoglobin will rise rapidly. Generally, clinically, methemoglobin greater than 500 for 4 weeks or methemoglobin 200-500 for 8 weeks needs to be alerted to the appearance of hepatocellular carcinoma. Other factors triggering elevated AFP, such as hepatitis, cirrhosis and chronic hepatitis, gastrointestinal tumors, postoperative embryonal tumors, etc., should be excluded, together with imaging data.