This study aimed to analyze the impact of sarcopenia on nutritional status in elderly patients with gastrointestinal tumors. We conducted a study of 146 elderly patients with gastrointestinal tumors in our hospital from January 2020 to June 2022. Patients enrolled were divided into normal nutritional status group (80 patients) and high nutritional risk group (66 patients) according to their nutritional status. The clinical information and nutritional status of the two groups were compared and analyzed. Multivariate logistic regression was done to analyze the risk factors of nutritional status in elderly patients with gastrointestinal tumors; and receiver operating characteristic (ROC) curve was used to evaluate the predictive value of sarcopenia on nutritional status in elderly patients with gastrointestinal tumors. Malnutrition was present in 66 (45.21%) of 146 elderly patients with gastrointestinal cancer. There was no significant difference in gender, age, and tumor location between the two groups (P> 0.05). However, statistically significant difference was observed between the two groups in terms of BMI, tumor staging, calf circumference, the third lumbar vertebra skeletal muscle index (L3-SMI), muscle strength, 6 m walking speed, short physical performance battery (SPPB) score, PG-SGA score, and sarcopenia (p< 0.05). The independent variables were set as BMI (≤ 21.27 kg/cm2), tumor staging (stage II to III), calf circumference (male: ≤ 30.01 cm, female: ≤ 29.37 cm), L3-SMI (male: ≤ 41.29 cm2/m2, female: ≤ 34.29 cm2/m2), muscle strength (male: ≤ 22.32 kg, female: ≤ 16.39 kg), 6 m walking speed (≤ 0.89 m/s), SPPB score (≤ 8.67 points), PG-SGA score (> 3 points), and sarcopenia. The dependent variable was malnutrition in elderly patients with gastrointestinal tumors. A univariate logistic regression analysis was conducted, showing that the influencing factors for malnutrition in elderly patients with gastrointestinal tumors were L3-SMI (male: ≤ 41.29 cm2/m2; female: ≤ 34.29 cm2/m2), muscle strength (male: ≤ 22.32 kg; female: ≤ 16.39 kg), BMI (≤ 21.27 kg/cm2), SPPB score (≤ 8.67 points), PG-SGA score (> 3 points) and sarcopenia. Moreover, the independent variables were set as L3-SMI (male: ≤ 41.29 cm2/m2; female: ≤ 34.29 cm2/m2), muscle strength (male: ≤ 22.32 kg; female: ≤ 16.39 kg), BMI (≤ 21.27 kg/cm2), SPPB score (≤ 8.67 points), PG-SGA score (> 3 points), and sarcopenia. The dependent variable was malnutrition in elderly patients with gastrointestinal tumors. The multivariate logistic regression analysis revealed that the influencing factors of malnutrition in elderly patients with gastrointestinal tumors were BMI (≤ 21.27 kg/cm2) and sarcopenia. The ROC curve of BMI (≤ 21.27 kg/cm2) and sarcopenia, and the area under the curve (AUC) of BMI (≤ 21.27 kg/cm2) and sarcopenia predicting malnutrition in elderly gastrointestinal cancer patients were 0.681 and 0.881, respectively. The influencing factors of malnutrition in elderly patients with gastrointestinal tumors were BMI (≤ 21.27 kg/cm2) and sarcopenia, and the two factors may exert predictive value in terms of the occurrence of malnutrition in such patients.