Abstract: Objective To identify the clinical value of blood and urine cystatin C (Cys C) in geriatric sepsis with acute kidney injury. Methods The clinical data of 76 elderly patients with sepsis in the Intensive Care Unit, Jianghan University Affiliated hospital were investigated retrospectively. Two groups were set up:AKI group (group 1) and non-AKI group (group 2). The clinical characteristics, laboratory and physiological indicators, and receiver operating characteristic curve were observed to predict the accuracy of Cys C and serum creatinine in the aspect of postoperative complications. Results Twenty-seven patients, who were diagnosed as AKI in 76 patients with geriatric sepsis, developed AKl and the incidence was 35.5%. Compared with group AKI with group none AKI, In AKI group, APACHEⅡ score (27.3±5.3 vs. 19.9±3.6, P=0.036), SOFA score (5.8±1.9 vs. 3.6±1.2, P=0.04) and pre-calcitonin (4.2±4.6 vs. 3.0±1.9, P=0.032) were higher, and MAP (60.1±3.1 vs. 72.1±4.2 mmHg, P<0.0 1) was lower than in non-AKI group. Blood Cys level (2.17±0.90 vs. 0.95±0.17 mg/L, P<0.01) and urine Cys level (1.81±0.99 vs. 0.41±0.19 mg/L, P<0.01) were obviously higher in AKI group than in non-AKI group. There was significant difference in serum creatinine (119.51±27.87 vs. 101.82±17.03, P=0.10) and mortality (18.5% vs. 6.1%, P=0.342) between two groups. According to the RIFLEF classification, acute renal injury was divided into three grades, including R (Risk) in 5 cases, accounting for 18.5%, I (injury) in 9 cases, accounting for 33.3%, F (failure) in 13 cases, accounting for 48.1%. The incidence of CRRT was 48.1%. The area of ROC for blood cystatin, urine cystatin and serum creatinine was 0.877, 0.867 and 0.592, respectively. Conclusions The combined used of blood Cys, Urine Cys and urine output can early predict the occurrence of AKI in geriatric sepsis.