Objective To determine the efficiency of structured triglycerides [STG, with the ratio of medium-chain triglycerides to long-chain triglycerides (MCT/LCT) accounting for 36% to 64%] for total parenteral nutrition (TPN) in the elderly patients with gastrointestinal (GI) tumor operation. Methods Sixty-eight elderly pathologically-identified GI tumor patients undergoing surgical treatment and then being admitted to the Department of Geriatrics of our hospital from January 2012 to October 2014 were recruited in this study. The cohort was randomly divided into 2 groups, STG group (n＝35) and MCT/LCT group (the ratio accounting for 50% to 50%, n＝33). They were all given TPN for 6 d after their operations. The parameters of nutrition, lipid metabolism, glucose metabolism, liver enzymes, bilirubin, high sensitivity C-reactive protein (hs-CRP) and immunologic profiles at baseline and 3 and 6d after treatment were measured and recorded respectively. Results There was no significant difference in the above-mentioned parameters between the 2 groups before and immediately after surgery. The levels of total protein (TP), albumin (ALB) and total cholesterol (TC) in the both groups, that of prealbumin (PAB) in the STG group, and that of low-density lipoprotein-cholesterol (LDL-C) in the MCT/LCT group were significantly increased after 6 days’ isonitrogen isocaloric nutritional support (P＜0.05). The nutritional parameters were significantly higher in the STG group than in the MCT/LCT group at the same time points (P＜0.05), but the levels of TC and LDL-C were remarkably lower in the former than in the latter. At 3d after treatment, the level of hs-CRP was reduced significantly in STG group compared to that of before treatment (P＜0.05), and the reduction was greater than that in the MCT/LCT group (P＜0.05). The CD3+ and CD4+ cell counts were increased significantly than before treatment in both groups (P＜0.05), but the counts of CD3+ and CD4+ cells and the ratio of CD4+/CD8+ were much higher in the STG group than in the partner one (P＜0.05). No statistical difference was seen in glucose levels, liver function and bilirubin level between the 2 groups after treatment (P＞0.05). Conclusion STG is superior to the conventional MCT/LCT in promoting protein synthesis, stabilizing lipid profiles, ameliorating the inflammatory reaction, as well as regulating the immune system, for TPN in the elderly patients after GI tumor operation, and also has higher safety in clinical application.