: Objective To investigate the relationship between preoperative neutrophil lymphocyte ratio (NLR) and other factors and postoperative nosocomial infection in children with congenital heart disease (CHD). Methods A total of 11937 children who underwent cardiac surgery from 2006 to 2017 were collected. According to the inflection point of NLR distribution with age and whether nosocomial infection occurred, the children with the age of score and abnormal LWR were independent protective factors for postoperative nosocomial infection in children≥224 days (P<0 . 05 ). The area under the curve (AUC) of NLR for predicting nosocomial infection in children <224 days was 0 . 594 ( 95 %CI: 0 . 572 ~ 0 . 617 ). When NLR>0 . 542 , its sensitivity and specificity for diagnosing nosocomial infection were 41 . 8 % and 73 . 6 %. Conclusion The postoperative infection rate of CHD children has decreased in recent years. Younger age, low BMI-Z score, preoperative infection, complex surgery, long operation time and increased NLR are the risk factors for postoperative infection in CHD children.