Methemoglobin is a specific tumor marker for detecting primary liver cancer. The normal value should be between 0-7ug/L, and the reference value varies significantly depending on the concentration of the reagents applied by the specific laboratory. If an abnormal increase of methemoglobin is found in daily physical examination, and active liver disease and pregnancy are excluded, malignant tumors of the liver should be highly suspected and further ultrasound examination of the liver should be performed, which can detect lesions smaller than 2 cm for experienced physicians. If there are obvious occupying images, further enhanced CT scan of the liver can be examined. After contrast injection, malignant tumors will show obvious fast-in and fast-out manifestations. Early diagnosis can be chosen for timely surgical treatment. The etiology is mainly due to chronic viral hepatitis or long-term alcohol consumption, resulting in alcoholic cirrhosis secondary to the disease.