Objective:To study the relationship between the dynamic changes of angiopoietin-2 (Ang-2) and surfactant protein D (SP-D) in pediatric acute respiratory distress syndrome (pARDS) and the severity and prognosis of the disease.Methods:Using nested case-control study method, 80 children with pneumonia complicated with pARDS admitted to PICU at Fujian Maternal and Child Health Hospital from June 2018 to May 2021 were selected as pARDS group, and 19 healthy children with corresponding age were selected as control group.According to the oxygenation, the children in pARDS group were divided into three subgroups: mild group (23 cases), moderate group (32 cases) and severe group (25 cases). According to the prognosis at discharge, the children in pARDS group were divided into survival group (67 cases) and death group (13 cases). Ang-2 and SP-D were detected by enzyme-linked immunosorbent assay.The levels of Ang-2 and SP-D in children with pARDS of different severity on the first day were compared; The changes of Ang-2 and SP-D levels on the 1st, 3rd and 8th day of children in survival group and death group were compared, and the receiver operating characteristic (ROC) curve was plotted to compare the predictive value of Ang-2 and SP-D for pARDS prognosis.Results:(1) The levels of Ang-2 and SP-D on the first day in pARDS group were significantly higher than those in control group( P<0.001). (2) The levels of Ang-2 and SP-D on the first day in children with pARDS of different severity levels were significantly different ( P<0.001), and the levels of Ang-2 and SP-D increased gradually with the increase of disease severity.(3) The levels of Ang-2 and SP-D in death group were significantly higher than those in survival group on the 1st, 3rd and 8th day ( P<0.05). (4) Prognostic efficacy of Ang-2 and SP-D levels in pARDS group at different time points: when the areas under the ROC curve predicted by Ang-2 on the 1st, 3rd and 8th day for inpatient mortality in children with pARDS were 0.808, 0.981 and 0.989, respectively; the optimal cut-off values were 6 000 pg/mL, 6 971 pg/mL and 4 171 pg/mL, respectively; the sensitivity was 84.6%, 92.3% and 92.3%, respectively; and the specificity was 76.1%, 97.0% and 98.5%, respectively.The areas under the ROC curve predicted by SP-D on the 1st, 3rd and 8th day for inpatient mortality in children with pARDS were 0.689, 0.993 and 0.983, respectively; the optimal cut-off values were 13544 pg/mL, 16003 pg/mL and 12294 pg/mL, respectively; the sensitivity was 84.6%, 100.0% and 100.0%, respectively; and the specificity was 46.3%, 98.5% and 97.0%, respectively. Conclusion:Serum Ang-2 and SP-D levels in children with pARDS increase with the aggravation of the disease.The dynamic changes of Ang-2 and SP-D in children with pARDS with different prognosis are different during the course of disease, and monitoring serum Ang-2 and SP-D during the course of disease has a certain predictive value for clinical outcome.