Objective To evaluate the accuracy of different biomarkers for early diagnosis of acute kidney injury (AKI) in the patients undergoing cardiovascular surgery under cardiopulmonary bypass (CPB). Methods A total of 200 patients, aged 22-86 yr, weighing 46-87 kg, scheduled for elective cardiovascular surgery under CPB, were enrolled in this study.The concentration of serum creatinine was determined at 1 day before operation and 1-7 days after operation.At 1 day before operation and 0, 2, 6 and 12 h after operation, the concentrations of urine neutrophil gelatinase-associated lipocalin (NGAL), cystatin C (Cys C), tissue inhibitor of matrix metalloproteinase type 2 (TIMP-2) and insulin-like growth factor binding protein-7 (IGFBP-7) were determined.The TIMP-2 and IGFBP-7 product (TI) was calculated.AKI was diagnosed after surgery according to Kidney Disease Improving Global Outcomes criteria.The receiver operating characteristic curve was plotted, and the area under receiver operating characteristic curve (AUC) was calculated. Results The incidence of AKI was 20.5%.The AUC of AKI diagnosed by the concentration of urine NGAL was 0.689, 0.709, 0.713 and 0.803 at 0, 2, 6 and 12 h after operation, respectively (P<0.05). The AUC of AKI diagnosed by the concentration of urine Cys C was 0.639, 0.762, 0.774 and 0.812 at 0, 2, 6 and 12 h after operation, respectively (P<0.05). The AUC of AKI diagnosed by TI was 0.687, 0.721, 0.740 and 0.779 at 0, 2, 6 and 12 h after operation, respectively (P<0.05). The AUC of AKI diagnosed by combined three indices the parallel test was 0.694, 0.773 and 0.794 at 0, 2 and 6 h after operation, respectively (P<0.05). The AUC of AKI diagnosed by the serial test was 0.610, 0.631 and 0.667 at 0, 2 and 6 h after operation, respectively. Conclusion Urine NGAL or Cys C concentrations or TI single detection and parallel test have a certain accuracy for early diagnosis of AKI in the patients undergoing cardiovascular surgery under CPB. Key words: Lipocalins; Matrix metalloproteinases; Insulin-like growth factor binding proteins; Cardiopulmonary bypass; Acute kidney injury