ObjectiveTo analyze impact of body mass index (BMI) on postoperative complications and disease-free survival (DFS) after hepatectomy for patients with hepatocellular carcinoma (HCC). MethodsIn total, 858 patients with HCC underwent hepatectomy were analyzed by retrospective cohort study. Patients were divided into two groups according to BMI:normal group (18.5 kg/m2 < BMI < 25.0 kg/m2) and obesity group (BMI≥25.0 kg/m2). The clinical and postoperative follow-up data were collected and statistically analyzed. Results① Compared with the normal group, the preoperative HBV-DNA loading was significantly lower (P<0.05), albumin was significantly higher (P<0.05), intraopera-tive blood loss was significantly increased (P<0.05), operation time, and the first portal hepatis occlusion time were signifi-cantly prolonged (P<0.05) in the obesity group. The postoperative complications and hospital stay had no significant differences between these two groups (P>0.05). ② The results of univariate analysis showed that the preoperative HBV-DNA≥ 104 U/mL, total bilirubin >21 μmol/L, albumin <35 g/L, grade B of Child-Pugh, intraoperative blood loss >500 mL, and operation time >240 min were associated with the postoperative complications after hepatectomy for patients with HCC (P<0.05). The results of multivariate analysis showed that preoperative total bilirubin >21 μmol/L, albumin <35 g/L, and operation time >240 min were the independent risk factors for postoperative complications (P<0.05). ③ Kaplan-Meier analysis showed that the 3-year DFS in the obesity group was significantly better than that in the normal group (P<0.05). The results of multivariate analysis showed that the major blood vessel tumor thrombi, multicenter tumor, tumor diameter ≥5 cm, and operation time >240 min were the independent risk factors for DFS (P<0.05), while the obesity was the protective factor for DFS (P<0.05). ConclusionFor HCC patients who receiving hepatectomy, obesity does not increase risk of postoperative complications, and could increase 3-year DFS. Thus preoperative improvement of nutritional status of patient with HCC has a great significance.