[Objective] To explore the correlation between the 5-factor modified frailty index (mFI-5) and acute kidney injury (AKI) after laparoscopic radical nephrectomy in elderly patients with renal cancer, so as to provide reference for the prevention and treatment of postoperative AKI. [Methods] A retrospective analysis was conducted on the clinical data of 214 elderly patients (≥60 years) who underwent laparoscopic radical nephrectomy at our hospital during Dec.2018 and Dec.2021.Patients were divided into frail group (n=75, mFI-5≥2) and non-frail group (n=139, mFI-5<2). The incidence of AKI and sub items of mFI-5 were compared between the two groups.According to the occurrence of AKI, patients were divided into AKI group (n=77) and non-AKI group (n=137). Univariate and multivariate logistic analyses were conducted to identify risk factors of AKI.Receiver operating characteristic (ROC) curves were plotted to test the effectiveness of mFI-5 in predicting AKI. [Results] The incidence of AKI was significantly higher in the frail group than in the non-frail group (64.00% vs. 20.86%, P<0.05). Univariate analysis showed that the incidence of AKI was related to gender, diabetes, hypertension, nonfunctional independent status, weakness and split kidney glomerular filtration rate (GFR). Multivariate logistic regression analysis showed that male (OR=2.454, 95%CI: 1.193—5.047), complicated weakness (OR=6.580, 95%CI: 3.380—12.811), and low split kidney GFR (OR=0.945, 95%CI: 0.911—0.980) were independent risk factors of AKI (P<0.05). The area under the ROC curve of AKI predicted by mFI-5 was 0.711. [Conclusion] Preoperative mFI-5 score is an effective predictor of AKI in elderly patients undergoing laparoscopic radical nephrectomy.As patients with frailty have a higher risk of AKI, preoperative evaluation and monitoring should be strengthened and timely intervention should be taken to improve the prognosis.