Objective to investigate the role of renal artery resistance index (RRI) in patients with sepsis complicated with acute kidney injury (AKI). Method Critically ill patients diagnosed from March 2014 -2017 year in February from ICU in 150 cases of sepsis as observation object, according to the KDIGO standards are divided into four groups, 51 cases without AKI as group A, 43 cases of AKI 1 as B group, 35 cases of AKI 2 as C group, 21 cases of AKI the 3 stage is the D group. The RRI patients were determined by ultrasound, Scys C and Ucys C by immunoturbidimetric assay, determination of SCr. of all the data were analyzed by ELISA. Result The group A 1D RRI, Scys C, Ucys C and SCr and B group were no significant difference, the 2、3d was significantly different; group C 1、2、3d RRI, Scys C, Ucys C and SCr were significantly higher than that in A group and B group D; group 1、2、3d RRI, Scys C, Ucys C and SCr were significantly higher than the other three groups; correlation analysis showed that RRI and Scys C, Ucys C and SCr each time were positively correlated. Conclusion Ultrasonography can effectively reflect the degree of renal damage in sepsis patients complicated with AKI.