Objective To explore the applicability of patient -generated subjective nutrition assessment PG-SGA prognostic nutrition index PNI and geriatric nutrition risk index GNRI in the nutritional assessment of elderly patients with digestive system tumors based on Global Leadership Initiative on Malnutrition criteria GLIM . Method Elderly patients who underwent digestive system tumor resection in Affiliated Hospital of Xuzhou Medical University from March 2021 to June 2022 were selected. With GLIM as the " gold standard" for the diagnosis of malnutrition PG-SGA PNI and GNRI were used for nutritional assessment and the sensitivity、 specificity、positive predictive value and negative predictive value were calculated and compared. The receiver operating characteristic ROC curve was plotted and the area under the curve AUC was compared by Delong test to explore the clinical value of each tool comparison between groups was conducted. Result The positive rate of malnutrition diagnosed by GLIM was 29. 3%. The positive rates of PG-SGA PNI and GNRI were 37. 0% 44. 0% and 45. 7% respectively. The body mass index muscle loss and phase angle indexes were worse in the patients with malnutrition and the serum albumin ALB prealbumin PA and hemoglobin HB indexes were decreased with statistical significance P < 0. 05 . Compared with GLIM standard PG - SGA showed the worst sensitivity 44. 1% and middle specificity 65. 9% with no diagnostic consistency Kappa = 0. 09 P = 0. 311 The sensitivity 61. 8% and specificity 63. 4% of PNI were average and there was weak agreement with GLIM diagnosis Kappa = 0. 22 P= 0. 013 . GNRI had the best specificity 88. 2% and sensitivity 72. 0% and had a good concordance with GLIM diagnosis Kappa = 0. 52 P<0. 001 . In the ROC curve GNRI had the highest predictive value AUC= 0. 817 95%CI = 0. 734-0. 882 followed by PNI AUC = 0. 621 95%CI = 0. 526 - 0. 709 . Delong test showed that the predictive value of GNRI and PG- SGA GNRI and PNI were statistically significant Z= 3. 83 4. 85 P < 0. 001 . The indexes of PA ALB TP and HB before、1 day after and 3-5 days after the surgery of the malnourished patients were significantly lower P<0. 05 . In addition the incidence of surgical site infection SSI was also higher in malnourished patients χ 2 = 5. 03 P = 0. 036 . Conclusion GNRI has shown good applicability in the nutritional assessment of elderly patients with digestive system tumors. In addition GNRI may be able to predict a patient's perioperative nutritional status and short-term prognosis.