Objective To evaluate and compare the abilities of different cut-off points of frailty index (FI) in the prediction of adverse outcomes for patients who have been discharged for 6 months. Methods A total of 312 elderly inpatients (≥70 years old) hospitalized in our hospital from July 2015 to December 2016 were enrolled, and their frailty was evaluated to calculate FI. Based on 3 different cut-off points of FI (FI-1:0.20-0.45; FI-2:0.20-0.35; FI-3:0.12-0.25), the patients were assigned into non-frailty, pre-frailty and frailty groups. All of them were followed up for at least 6 months, and were divided into adverse outcome group and no adverse outcome group according to the adverse outcomes (falls, fractures, readmission and death). SPSS statistics 18.0 was used to perform the statistical analysis. Student′s t test or Chi-square test was employed for comparison between groups based on different data types. Cox regression model and area under receiver operating characteristic (ROC) curves (AUC) were used to evaluate the predictive abilities of different cut-off points of FI for adverse outcomes. Results The range of FI values was 0.06 to 0.61 in the 312 patients, and the incidence of frailty with different cut-off points of FI (FI-1:FI≥0.45; FI-2:FI＞0.35; FI-3:FI≥0.25) was 13.5%, 25.3% and 54.2%, respectively. For those having been discharged for over 6 months, 146(46.8%) of them experienced adverse outcomes, including falls in 31(9.9%), fractures in 12(3.8%), readmission in 123(39.4%), and death in 16 patients (5.1%). The patients with adverse outcomes had older age, larger number of comorbidities, and higher incidences of coronary heart disease, chronic kidney disease, atrial fibrillation, and chronic obstructive pulmonary disease when compared with those without adverse outcomes (P<0.01).After adjustment of age, gender, and number of comorbidities, frailty determined by critical value of FI-1 was an independent predictor for adverse outcomes in the elderly inpatients (HR=2.38,5%CI 1.35-4.19,P=0.003), while that determined by FI-2 (HR=1.63,5%CI 0.96-2.77,P=0.068) and FI-3 (HR=1.54, 95%CI 0.56-4.25,P=0.406) was not associated with the adverse outcomes. The AUC of FI-1,FI-2 and FI-3 which were used to predict adverse outcomes of elderly inpatients who were discharged after 6 months was 0.685,0.673 and 0.644, respectively (P＜0.05), and was 0.747,0.731 and 0.647, respectively when they were used to predict the mortality (P＜0.05).Conclusion FI can predict adverse outcomes in elderly inpatients who have been discharged for over 6 months.The predictive ability is associated with the cut-off point of FI that determines the frailty, with those of FI≥0.45(FI-1) and FI＞0.35(FI-2) better than that of FI≥0.25(FI-3). The former 2 cut-off points also are good at predicting mortality.