Objective The aim of this study was to evaluate the relationship between renal resistive index(RI)and power Doppler ultrasound(PDU). The effectiveness of each method to predict acute kidney injury(AKI)also was compared.  Methods Forty enrolled patients were divided into three groups by KDIGO guideline: sepsis group, AKI 1 group, AKI 2 group and AKI 3 group, with 10 patients in each group. Renal RI and 4-level semiquantitative PDU score were recorded; AKI stage and RI/PDU were compared; the co-variables of death were also analyzed. Results There were statistical differences for PDU score in the AKI 1 group, AKI 2 group and AKI 3 group, and RI of AKI 3 group was higher than that in the other three groups. Furthermore, PDU score was significantly correlated with SCr level and CRRT treatment days. APACHEⅡ score, heart rate and SCr were closely correlated with death. Conclusion Compared with RI, PDU score maybe better to monitor the severity of AKI, but both have no correlation with the prognosis of AKI.