Objective:To investigate the effect of plasma Glypican-4 level on the prognosis of children with pneumonia and acute respiratory distress syndrome(ARDS) and its predictive value.Methods:From April 2018 to April 2021, 92 children with pneumonia and ARDS admitted to the PICU of Baoding First Hospital for the first time were selected as the pneumonia+ ARDS group, 87 children with pneumonia admitted to the Pediatrics Department of this hospital were selected as the pneumonia group, and 95 children for physical examination in the same hospital were selected as control group.The pediatric critical illness score(PCIS)was used to score the children in pneumonia+ ARDS group and pneumonia group.The enzyme-linked immunosorbent assay(ELISA)method was used to detect the levels of Glypican-4 in plasma of three groups.Receiver operating characteristic(ROC) curve was used to evaluate the diagnostic value of plasma Glypican-4 in pneumonia complicated with ARDS, and the prognosis-related factors was analyzed by the Cox risk regression model.Results:The heart rate, pneumonia history, 28-day mortality rate, and plasma Glypican-4 in the pneumonia+ ARDS group were significantly higher than those in control group and pneumonia group, and PCIS score in pneumonia+ ARDS group was lower than that in pneumonia group ( P<0.05). According to the prognosis of pneumonia+ ARDS group on 28 days, the children were divided into survival group (74 cases) and death group (18 cases). Compared with the survival group[(3.92±0.31)μg/L], the plasma Glypican-4 level in death group[(4.78±0.35)μg/L] increased, whose difference was statistically significant( t=10.292, P<0.001). ROC curve analysis results showed that the area under the ROC curve of Glypican-4 predicting the prognosis of children with pneumonia combined with ARDS was 0.92, whose sensitivity was 94.2% and specificity was 88.3%, as well as the cut-off value was 4.11 μg/L.Multivariate Cox analysis showed that Glypican-4 level(high expression), heart rate (high frequency) and the history of pneumonia were prognostic risk factors affecting the prognosis of children with pneumonia and ARDS( P<0.05). Conclusion:The level of plasma Glypican-4 in children with pneumonia and ARDS significantly increased, and it is closely related to the prognosis of children with pneumonia and ARDS, and has high predictive value for the prognosis of children with pneumonia and ARDS.