Objective To investigate the incidence and risk factors of acute kidney injury (AKI)in hepatitis B virus (HBV)related acute-on-chronic liver failure (ACLF)patients,and to explore the impact of AKI on the prognosis of ACLF.Methods The medical records of 227 patients who were diagnosed with HBV-related ACLF at the Department of Infectious Diseases in the First Affiliated Hospital of Nanchang University from January 2015 to August 2016 were retrospectively reviewed.Patients were divided into AKI group and non-AKI group based on the AKI criteria published by International Club of Ascites in 2015 .Demographic and clinical data were compared between groups.The AKI incidence and its impact on patients’prognosis were analyzed.The comparison of continuous variables was done by t test or rank-sum test.The comparison of categorical variables was done byχ2 test or Fisher exact test.AKI risk factors were analyzed by using logistic regression.Results There were 66 (29.1 %)cases were diagnosed with AKI among 227 ACLF patients,among which,45 patients (68.2%)were stage Ⅰ,14 (21 .2%) were stage Ⅱ and 7 (10.6%)were stage Ⅲ.Age,cirrhosis,concentrations of total bilirubin and albumin,international normalized ratio (INR),percentage of neutrophils,MELD scores and spontaneous peritonitis rate (SBP)were all statistically different between AKI group and non-AKI group (all P <0.05).The binary logistic regression analysis revealed that only INR (OR=3.132,P =0.001 )and SBP (OR=4.204,P =0.001 )were the independent risk factors of AKI.The optimal cut-off value for INR was 2.025 with AUROC of 0.609 (P =0.01),sensitivity of 59.1 % and specificity of 62.1 %.The 30-day mortality of AKI group was significantly higher than non-AKI group (χ2= 18.324,P < 0.01). Conclusions AKI is relatively common in patients with ACLF.The risk factors of AKI are INR and SBP. AKI has significant impact on the short-term survival rate of ACLF.Therefore,physicians should pay attention to patients with INR of ACLF at admissions and SBP during the management so as to prevent the occurrence of AKI and to reduce the fatality of ACLF.