Objective To assess the nutritional status in elderly patients with chronic renal insufficiency (CRI) and reveal the key factors affecting the nutritional status. Methods A total of 310 elderly patients with CRI who received hospitalization treatment and outpatient follow-up in the hospital from January 2021 to June 2024 were selected as the investigation subjects. The nutritional status of patients was evaluated by mini-nutritional assessment (MNA) questionnaire, and the nutritional status and dietary structure of patients were comprehensively evaluated by anthropometric indicators [height, weight, body mass index (BMI), upper arm circumference, calf circumference], biochemical indicators [serum albumin (ALB), prealbumin (PA), hemoglobin (Hb), transferrin (TF)] and 24-hour dietary review method. According to the investigation results of nutritional status, the patients were divided into good nutrition group (MNA score≥24 points), nutritional risk group (MNA score of 17-23.5 points) and malnutrition group (MNA score<17 points). Univariate analysis was adopted to screen the potential influencing factors of elderly CRI. Multivariate logistic regression model was applied to analyze the influencing factors of malnutrition in elderly CRI patients. Results Among the 325 questionnaires were distributed, but only 310 valid questionnaires were recovered, with an effective recovery rate of 95.38%. Investigation results revealed that among the 310 patients, 29.35% (91 cases) had good nutritional status, and 42.26% (131 cases) had nutritional risk, and 28.39% (88 cases) had malnutrition. Univariate analysis indicated that there were statistical differences in BMI, CRI staging, serum ALB, PA, Hb, TF, protein intake and total calorie intake among the good nutrition group, the nutritional risk group and the malnutrition group (P<0.05). Multivariate logistic regression analysis suggested that low BMI (OR=0.903, 95%CI: 0.867-0.941), high CRI stage (OR=1.091, 95%CI: 1.053-1.130), low serum ALB (OR=0.907, 95%CI: 0.867-0.948), PA (OR=0.918, 95%CI: 0.888-0.949), Hb (OR=0.944, 95%CI: 0.909-0.997), TF (OR=0.912, 95%CI: 0.874-0.952), insufficient protein intake (OR=0.924, 95%CI: 0.882-0.969) and insufficient total calorie intake (OR=0.938, 95%CI: 0.909-0.968) were influencing factors for malnutrition in elderly patients with CRI (all P<0.05). Drawing ROC curve of malnutrition in elderly patients with CRI according to the prediction probability of logistic regression model found that the AUC, sensitivity, specificity, 95%CI and Youden index were 0.976, 93.18%, 92.34%, 0.953-0.990 (P<0.05) and 0.855. Conclusion The incidence rate of malnutrition is high in elderly patients with CRI, and is mainly affected by factors such as low BMI, high CRI stage, low serum ALB, PA, Hb and TF levels and insufficient protein and total calorie intakes. In addition, logistic regression model has high predictive value and can provide a reference for early clinical identification of high-risk population with malnutrition among elderly patients with CRI.