Objective To investigate the effect of intraoperative renal artery resistance index(RI)in predicting postoperative acute kidney injury(AKI)in patients undergoing cardiac surgery with cardiopul-monary bypass(CPB).Methods Forty-four patients undergoing elective cardiac surgery with CPB,21 males and 23 females,aged ≥18 years,BMI 18.5-30.0 kg/m2,ASA physical status Ⅰ-Ⅲ,were select-ed.Left renal artery peak systolic velocity(PSV)and end-diastolic velocity(EDV)were measured by transesophageal echocardiography(TEE)20 minutes after general anesthesia induction(T1)and 30 minutes after CPB cessation(T2).RI was calculated as(PSV-EDV)/PSV.Patients were divided into two groups:the AKI group and the non-AKI group,according to whether occurred AKI by the diagnostic criteria of the kidney disease:improving global outcomes organization(KDIGO).Logistic multivariate regression analysis was performed to identify the risk factors for AKI occurrence.Results Sixteen patients(36％)oc-curred AKI.Compared with the non-AKI group,the CPB duration and aortic cross-clamp duration were sig-nificantly prolonged(P＜0.05),the renal artery RI at T,and T2 were significantly increased in the AKI group(P＜0.05).Multivariate logstic analysis showed that RI at T2 was an independent risk factor for AKI occurrence after cardiac surgery,the AUC was 0.893(95％CI 0.794-0.991,P＜0.010),the sensitivity and specificity were 84.5％and 78.6％,respectively,and the cut-off value was 0.720.Conclusion Intra-operative renal artery RI in patients undergoing cardiac surgery is an independent risk factor for AKI after cardiac surgery,and renal artery RI＞0.720 at 30 minutes after CPB cessation can serve as a predictive in-dicator for AKI after cardiac surgery.