Objective To observe the delirium of the elderly inpatients and analyze the related risk factors. Methods A total of 365 patients aged ≥80 years were selected, who were admitted to the Geriatric Department of Affiliated Hospital of Xuzhou Medical University from February 2018 to February 2020. On admission the patients were assessed using the comprehensive geriatric assessment(CGA), and the incidence of delirium was assessed within 7 days after admission using the confusion assessment method (CAM). The patients were divided into delirium group(n=43) and non-delirium group(n=322) by CAM. SPSS statistics 24.0 was used for data analysis. Depending on the data type, t-test or χ² test were used for comparison between groups. Logistic regression analysis was used to analyze the independent risk factors. Results Of 365 elderly patients, 43 developed delirium with an incidence of 11.8%. The delirium group differed significantly from the non-delirium group in home environment, living style, polypharmacy rate, depression, malnutrition rate, coexistence rate, frail status, mini-mental state examination (MMSE) score, geriatric syndrome and serum central nervous system specific protein (S100β) level on admission (P<0.05). Multivariate logistic regression analysis showed that age (OR=2.683,95%CI 1.005-4.019; P<0.05), nutritional status (OR=2.212,95%CI 1.101-5.212; P<0.05), frailty (OR=3.108,95%CI 1.005-5.015; P<0.05), MMSE score (OR=2.694,95%CI 0.705-3.117; P<0.05), number of geriatric syndromes (1.412, 95%CI 1.025-4.041; P<0.05), S100β(OR=1.919,95%CI 1.789-4.664; P<0.05) were all independent risk factors of delirium. Conclusion The incidence of delirium in the elderly inpatients is related to nutritional status, frailty, cognitive impairment and the increase of S100β protein, which requires clinical attention and intervention.