Background <p>This study aimed to investigate the prevalence and influencing factors of preoperative anaemia in Chinese children with congenital heart disease (CHD), as well as its implications for clinical management and postoperative outcomes.​</p> Methods <p>A cross-sectional study was performed using a pediatric CHD database from Central China. We calculated the prevalence and proportion of anaemia in different subgroups and genders. A visualization of the distribution of hemoglobin in males and females of different age groups was then plotted. Multivariate logistic regression model and forest plots were used to identify influencing factors (presenting odds ratios [OR] and 95% confidence intervals [CI]), and the relationship between preoperative anaemia and postoperative prognosis was evaluated.​​</p> Results <p>A total of 12,294 CHD patients were included, with an overall anaemia prevalence of 41.5%. The neonate was the most critical period (52.5% prevalence), and higher rates were observed in complex CHD (47.2%), low birth weight (LBW, 69.1%), and rural patients (45.3% vs. 37.1% in urban areas). Double-outlet right ventricle (DORV) was most strongly associated with anaemia. Median hemoglobin levels in both genders were below age-specific standards. Preoperative anemia was associated with adverse postoperative outcomes.</p> Conclusions <p>Preoperative anaemia is highly prevalent in Chinese CHD children, particularly in high-risk subgroups. These findings emphasize the clinical necessity of early screening and targeted intervention to improve postoperative outcomes and quality of life. Future prospective longitudinal studies are warranted to comprehensively elucidate the long-term association between anaemia and CHD across the lifespan.</p>