To analyze the relationship between frailty index and 25(OH) vitamin D in elderly inpatients. Totally 300 elderly patients in the geriatric department of Yuncheng Central Hospital from December 2019 to November 2020 were enrolled. There were 100 cases of non-frailty, pre-frailty, and frailty, respectively. The incidence of frailty was higher in patients with low household income, more diseases, less education, more medication, poor health self-assessment, and older age. There were statistical differences in vitamin D levels in weight loss, slower walking pace, reduced grip strength, decreased physical performance, and fatigue. There were significant differences in hypertension, diabetes mellitus, cerebral apoplexy, osteoporosis, and multiple chronic diseases among the three groups. The correlation analysis of senile frailty with age, weight, education level, income, BMI, combined chronic diseases, waist-to-hip ratio, weight loss, slower pace, decreased grip strength, decreased physical fitness, fatigue, and vitamin D level was statistically significant. Factors, included age, weight, education level, income, BMI, combined chronic diseases, waist-to-hip ratio, weight loss, slower pace, decreased grip strength, decreased physical fitness, fatigue, vitamin D level had a significant effect on frailty. Logistic regression analysis showed that vitamin D and age were independent influencing factors for frailty.