Abstract: Objective:To explore the expression and clinical significance of circular RNA hsa_circ_0001801 in children with pulmonary arterial hypertension (PAH) associated with congenital heart disease (CHD).Methods:The whole blood samples of 30 children with CHD and 30 children with PAH-CHD were collected, and the whole blood samples of 14 healthy children were collected as the control group.The expression levels of hsa_circ_0001801 in different groups were detected by real-time fluorescence quantitative polymerase chain reaction (RT-qPCR), correlation analysis was performed with the clinical data, and the influencing factors for PAHCHD were determined by Logistic regression analysis.Results:The relative expression level of hsa_circ_0001801 in PAH-CHD group was lower than that in control group and CHD group(P< 0.05), while there was no significant difference between CHD group and control group.Spearman correlation analysis showed a positive correlation between the expression of hsa_circ_0001801 and creatine kinase-MB (CK-MB) (r=0.393, P=0.002); multivariate Logistic regression analysis showed hsa_circ_0001801 was a protective factor for PAH-CHD (OR=0.465, 95% CI:0.257-0.844, P=0.012).Conclusion:hsa_circ_0001801 is aberrantly expressed in whole blood of children with PAH-CHD and has potential as a biomarker for PAH-CHD.