Abstract: Objective To investigate the changes in Doppler flow velocity curve parameters of the main pulmonary artery in fetuses of pregnant women with early-onset severe preeclampsia and their predictive value for fetal lung maturity. Methods Thirty pregnant women with early-onset severe preeclampsia were selected as study group and further divided into respiratory distress syndrome (RDS) group (n=17) and non-RDS group (n=13) based on neonatal outcomes. Additionally, 80 pregnant women with normal pregnancies undergoing antenatal examination during the same period were selected as normal control group. Doppler flow velocity curve parameters of the mainpulmonary artery in fetuses of pregnant women in each group were compared, and the predictive value of these parameters for neonatal RDS was analyzed. Results The systolic acceleration time (AT) and systolic ejection time (ET) of fetuses in the study group were shorter than those in the control group, and the ratio of AT to ET (AT/ET) was lower than that in the control group (P<0.05). The AT and ET of fetuses in the RDS group were shorter than those in the non-RDS group (P<0.05), but there was no statistically significant difference in AT/ET between the two groups (P>0.05). Binary Logistic regression analysis revealed that the combined predictive equation for neonatal RDS using these three parameters was logit(P)=AT+(-0.560/1.048)×ET+(-2.464/1.048)×AT/ET. Receiver operating characteristic curve analysis showed that the areas under the curve for AT, ET, AT/ET alone and their combination for predicting neonatal RDS were 0.837, 0.877, 0.712, and 0.929, respectively, with sensitivities of 94.1%, 94.1%, 47.1%, and 94.1%, and specificities of 58.1%, 75.3%, 84.9%, and 78.5%, respectively. Conclusion The Doppler flow velocity curve parameters including AT, ET, and AT/ET of the main pulmonary artery in fetuses of pregnant women with early-onset severe preeclampsia are decreased. Doppler ultrasonography can effectively evaluate fetal lung maturity by monitoring the flow velocity curve of the main pulmonary artery.