Methemoglobin is a glycoprotein. The quantitative test of methemoglobin is to determine the specific amount of methemoglobin, which is more accurate compared to the qualitative test of methemoglobin and is beneficial for clinical disease determination. Methemoglobin is currently used in clinical practice mainly for screening and diagnosis of primary liver cancer, and also for postoperative monitoring of primary liver cancer. However, active liver disease, cirrhosis, germinal embryonic tumors and pregnant women may all have elevated AFP, and at this time, a simple qualitative AFP test may be positive, making it difficult to determine the specific cause. If fetoprotein value is greater than 400ug/L and is persistently elevated, the possibility of primary hepatocellular carcinoma is very high, and further liver imaging, especially enhanced CT or MRI of the liver, can be performed to further clarify the cause.