This study develops and validates a predictive model for perioperative red blood cell transfusion (PRT) risk in pediatric cardiac surgery with cardiopulmonary bypass (CPB). Using data from 19,155 children, eight key predictors—including age, weight, preoperative hemoglobin, CPB duration, and cyanotic congenital heart disease—were identified. The nomogram demonstrated high accuracy (AUC 0.886) and clinical utility, aiding personalized blood management strategies to optimize outcomes and reduce transfusion risks.