Objective To analyze the evaluation value of dynamic monitoring of changes in serum brain natriuretic peptide （BNP）， urinary kidney injury molecule-1 （KIM-1）， and serum cystatin C （CysC） levels in acute kidney injury （AKI） after pediatric heart surgery. Methods 138 children who underwent cardiopulmonary bypass for congenital heart disease correction in our hospital from January 2023 to June 2024 were selected. The incidence of postoperative AKI in children was counted and they were divided into the AKI group and the non-AKI group accordingly. The changing levels of serum BNP， KIM-1， and CysC in the two groups of children were dynamically monitored and compared. The receiver operating characteristic curve （ROC） was used to evaluate the occurrence and severity of AKI after pediatric heart surgery. Results Among the 138 children， 81 did not develop AKI and 57 developed AKI， with an incidence rate of 41.30%. In the AKI group， there were a mild group （n = 20） and a moderate-severe group （n = 37）. Regarding the AKI group and the non-AKI group： there were differences in the levels of BNP， KIM-1， and CysC at 6 h， 12 h， 24 h， and 48 h after surgery （P < 0.05）. The levels of BNP， KIM-1， and CysC in the AKI group were higher than those in the non-AKI group （P < 0.05）， and there were differences in the changing trends of BNP， KIM-1， and CysC levels between the two groups （P < 0.05）. The results of multivariate Logistic regression analysis showed that BNP， KIM-1 and CysC were all factors influencing the occurrence of AKI after pediatric cardiac surgery （P < 0.05）. The ROC curve showed that the AUC of the three combined to predict the occurrence of AKI after pediatric heart surgery was 0.893， which was significantly higher than 0.723， 0.812， and 0.761 of BNP， KIM-1， and CysC respectively. Regarding the mild group and the moderate-severe group： there were differences in the levels of BNP， KIM-1， and CysC at 6 h， 12 h， 24 h， and 48 h after surgery （P < 0.05）. The levels of BNP， KIM-1， and CysC in the mild group were lower than those in the moderate-severe group （P < 0.05）， and there were differences in the changing trends of BNP， KIM-1， and CysC levels between the two groups （P < 0.05）. The results of multivariate Logistic regression analysis indicated that BNP， KIM-1 and CysC were all factors influencing the severity of AKI after pediatric cardiac surgery （P < 0.05）. The ROC curve showed that the AUC of the three combined to evaluate the severity of AKI was 0.908， which was significantly higher than 0.780， 0.762， and 0.720 of BNP， KIM-1， and CysC respectively. Conclusion Dynamic monitoring of changes in serum BNP， KIM-1， and CysC levels has a high evaluation value for the occurrence and severity of AKI after pediatric heart surgery， and the combined detection has a higher evaluation value.