Objective To explore the risk factors of frailty in the elderly with type 2 diabetes mellitus (T2DM). Methods A total of 310 elderly T2DM patients who admitted to the Department of Endocrinology, XuanWu Hospital of Capital Medical University, were included in the study. The levels of fasting glucose, fasting insulin, glycosylated hemoglobin(HBA1c), blood lipid and 25-hydroxyvitamin D₃ (25-OHD₃) were measured, and the past histories were recorded. The mini-nutritional scale (MNA) for nutritional status assessment was used to assess the nutritional status, and the FRAIL scale to assess frailty. The patients were divided into three groups based on frailty. SPSS statistics 20.0 was used for data analysis. Depending on the data type, χ² test, Fisher exact probability method, analysis of variance, LSD test and rank sum test were used for comparison between groups. Results There were 45 patients in the frail group, 132 in the pre-frail group, and 133 in the normal group. Age, risk of malnutrition and stroke in the frail group were significantly higher than those in the normal group,but the glomerular filtration rate and 25-OHD3 levels were significantly lower (P＜0.05). The multivariate logistic regression analysis showed that having risk of malnutrition and stroke were independent risk factors of frailty in the elderly with T2DM (OR=3.80,2.38; P＜0.05), and 25-OHD₃ level was a protective factor of frailty (OR=0.91, P=0.001). Conclusions Having risk of malnutrition and stroke increases the risk of frailty in the elderly with T2DM, and high 25-OHD₃ level decreases the risk of frailty.