Liver cancer patients often need liver function tests, the purpose of which is not to diagnose liver cancer, but to understand the degree of liver function damage and to use it to formulate treatment plans for liver cancer patients. Most liver cancer patients have normal liver function because liver cancer is not a diffuse liver damage like hepatitis and cirrhosis, but a relatively limited lesion. Because the liver has strong reserve function, even if most of the liver is invaded by liver cancer, as long as the remaining liver is not severely damaged, it can still compensate liver function and does not show abnormal liver function. In advanced stage liver cancer patients, the invasion of liver by hepatocellular carcinoma has caused the remaining normal liver cells to be very few and the liver function can no longer be compensated, thus showing abnormal liver function. Thus, liver cancer cannot be ruled out because of normal liver function, and liver cancer cannot be diagnosed because of abnormal liver function.