Objective: To identify the risk factors for early fluid overload(FO)following repair in the pediatric patients with anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) complicated with moderate or severe left ventricular dysfunction (left ventricular ejection fraction [LVEF]<50%) and evaluate the effect on clinical outcomes. Methods: Forty-three pediatric patients with ALCAPA complicated with moderate or severe left ventricular dysfunction, aged 2-128 months, weighing 4.5-34.5 kg, with New York Heart Association Ⅲ or Ⅳ, undergoing ALCAPA repair, were enrolled in this study.The pediatric patients were divided into FO≥5% group (n=14) and FO<5% group (n=29) according to the FO developed within 24 h after operation. The pediatric Risk, Injury, Failure, Loss, and End-Stage Renal Disease criterion was used to diagnose acute kidney injury developed after operation. Factors including age, height, weight, preoperative LVEF, preoperative biomarkers, operative data, postoperative ventilation time, duration of intensive care unit(ICU)stay and related postoperative clinical outcome parameters were recorded.The risk factors of which P values were less than 0.05 would enter the multivariate logistic regression analysis to stratify the risk factors for FO≥5% developed within 24 h after operation.The effect of FO≥5% on postoperative severe acute kidney injury (Injury and Failure), ventilation time, duration of ICU stay and etc. was assessed. Results: Fourteen cases developed early postoperative FO≥5%, and the incidence was 33%.The results of the logistic regression analysis showed that lower preoperative LVEF was an independent risk factor for early postoperative FO≥5% (P<0.05). Compared with FO<5% group, the postoperative ventilation time and duration of ICU stay were significantly prolonged, the number of pediatric patients who developed pulmonary infection and required reintubation was increased, the number of pediatric patients in whom duration of ICU stay was more than 14 days was increased (P<0.05), and no significant change was found in the other parameters of clinical outcomes in FO≥5% group (P>0.05). Conclusion Lower preoperative LVEF is a risk factor for early postoperative FO in pediatric patients with ALCAPA complicated with a moderate or severe left ventricular dysfunction undergoing repair, and it is not helpful for clinical outcomes in pediatric patients when postoperative early FO≥5% occurs.