Primary liver cancer is the fourth most common malignancy and third most frequent cancer-related cause of death in China. Hepatectomy is a radical treatment for primary liver cancer. Advancement in surgical techniques and perioperative managements have apparently improved the safety of hepatectomy. However, the posthepatectomy liver failure caused by the insufficient residual liver function is still the main reason of perioperative death. Therefore, it is essential to assess hepatic functional reserve before hepatectomy. There are several examinations to assess hepatic function, including traditional blood tests, the Child‐Pugh score, model for end-stage liver disease (MELD) score, indocyanine green (ICG), ultrasound, computed tomography volumetry, Gd-EOB-DTPA MRI and nuclear medicine. Although the Child-Pugh score is the most widely used model in evaluating hepatic function, its predictive value is limited. According to the Child‐Pugh classification, the majority of patients are classified as grade A, but their liver functions may vary significantly. MELD was originally used to predict survival in patients after transjugular intrahepatic portosystemic shunt and has been used as a tool for ranking candidates for transplantation, but cannot determine the scope of liver resection. The indocyanine green and other metabolic quantitative liver function tests can evaluate functional hepatocytes, making them more accurate in predicting liver function. Ultrasound is a non-invasive method that has been proposed for the assessment of the degree of hepatic fibrosis in patients with chronic liver diseases by measuring liver stiffness and indirectly predict liver function. CT volumetry can provide anatomic information on the remnant liver volume but not on functional volume. In addition, its use is limited by radiation, especially when repetitive examinations are required. Arterial enhancement fraction can detect the presence of mild, moderate, and advanced liver fibrosis. Gd-EOB-DTPA is a paramagnetic hepatobiliary magnetic resonance contrast agent having the same transport mechanisms like ICG. Therefore, similar to ICG clearance, Gd-EOB-DTPA MRI should provide information for quantitative evaluation of liver function and allow for anatomic delineation of hepatic function. 99mTC-GSA, combined with single photon emission computed tomography, CT and three-dimensional reconstruction, may be a better quantitative measure of liver function, especially for damaged livers with functional heterogeneity among the hepatic segments. 99mTc mebrofenin hepatobiliary scintigraphy in combination with single-photon emission computed tomography/computed tomography is increasingly applied for the quantitative assessment of liver function before liver surgery. This dynamic quantitative liver function test allows assessment of both total and regional liver function, represented by the hepatic mebrofenin uptake rate, thereby assisting in adequate patient selection. Assessing hepatic functional reserve before hepatectomy is beneficial to reduce the incidence of post hepatectomy liver failure. However, it is difficult to accurately evaluate liver function before surgery because of the limitations of the liver function tests available. Here, the authors analyze above methods and their advantages.