Abstract: Objective：To evaluate the influence of body mass index (BMI) on the long- term prognosis of liver cancer patients after hepatectomy. Methods：Totally, 596 patients were enrolled with 388 hepatocellular carcinoma (HCC) cases and 208 intrahepatic cholangiocellular carcinoma (ICC) cases. Patients were divided into three groups according to the BMI: underweight group (BMI＜18.5 kg/m2), normal group (18.5 kg/m2≤BMI＜25 kg/m2), and overweight/obesity group (BMI≥25 kg/m2). Patients’ clinical features and follow- up data were collected. Kaplan- Meier curve was applied for survival analysis, and Cox regression model was used for univariate and multivariate analysis. Results：In both HCC and ICC cases, the overall survival rate (OS) was significantly lower in the underweight group than that in the other two groups (P<0.05). In HCC cases, the cumulative recurrence rate (CRR) was higher in the underweight group (P<0.001). In ICC cases, there was no statistical difference in CRR among the three groups,but showed similar trend with HCC patients. The OS and CRR had no statistical difference between the normal and overweight/obesity groups. The multivariate analysis indicated that BMI＜18.5 kg/m2 was an independent prognostic factor for OS and CRR in HCC patients after surgery (P<0.05). Conclusions：Underweight patients had worse OS and higher CRR, whereas overweight and obesity might not affect the post- operative prognosis of liver cancer patients after hepatectomy. Simply using BMI has its limitation as a factor of nutrition status to evaluate the prognosis of liver cancer patients after hepatectomy.