Objective To compare the frailty index of accumulative deficits (FI-CD), frailty phenotype (FP), frailty scale (FS), and clinical frailty scale (CFS) in evaluating frailty in the elderly inpatients and predicting their all-cause mortality after discharge from hospital. Methods In a cohort study, FI-CD, FP, FS, and CFS were used for frailty assessment. The subjects were followed up for over 3 months after discharge with death denoted as the observation endpoint. The Cox regression model was employed for assessing the relationships between frailty identified by different assessment methods and all-cause mortality, and the receiver operating characteristic (ROC) curve for comparing their predictive ability of death. Results Totally, 630 patients aged ≥65 years were recruited in the present study, of whom 14 were lost to follow-up. The average follow-up time was 24.8 months. The frailty evaluated by FI-CD, FP, FS and CFS were 31.7%, 33.8%, 23.5% and 23.5%, respectively, with 90 deaths (14.6%). In the Cox regression model adjusted for age, sex and other variables, FI-CD, FP, FS and CFS identified an increased risk of death after discharge in the frail patients against non-frail patients (HR=5.78,6.21,2.16 and 5.61; 95%CI 2.40-13.90,2.18-17.68,1.12-4.17 and 3.11-10.11 respectively, all P＜0.05). After adjustment for age and sex, pre-frailty as determined by FI-CD, FP and CFS was significantly associated with the increased risk of death (HR =2.96,3.93 and 2.58; 95%CI 1.22-7.22,1.38-11.14 and 1.36-4.92, P=0.017,0.010 and 0.004, respectively). Area under the ROC curves (AUC) for FI-CD, FP, FS, and CFS for death prediction were 0.726,0.684,0.621 and 0.750, respectively (all P<0.001). Conclusion The assessed rates of frailty ranged from 23.5% (FS, CFS) to 33.8% (FP). Frailty is a risk factor of death. FI-CD and CFS are able to predict death in the elderly inpatients, and CFS outperforms the other methods.