Abstract:〔Abstract〕 Objective To investigate the effect of pulmonary surfactant under mechanical ventilation in the treatment of neonatal pneumonia complicated with respiratory failure. Methods 80 children with neonatal pneumonia complicated with respiratory failure in the Neonatology Department of Wuxi Children's Hospital from February 2017 to February 2022 were retrospectively selected. According to the treatment method, they were divided into two groups: the treatment group (observation group) and the mechanical ventilation treatment group (control group), with 40 cases each. The differences between the two groups in blood gas index, mean arterial pressure (MAP), respiratory mechanics index, mechanical ventilation time, total oxygen uptake time, hospital stay and complications were analyzed. Results Before treatment, arterial partial oxygen pressure (PaO2), oxygenation index (PaO2/FiO2), arterial partial carbon dioxide pressure (PaCO2), hydrogen ion concentration index (pH), MAP, positive end expiratory pressure (PEEP), plateau pressure (Pplat), and peak airway pressure (PIP) were compared between the two groups, there was no statistical significance (P > 0.05). After treatment, PaO2, PaO2/FiO2 in the two groups were higher than before treatment, and PaCO2, MAP and PEEP were lower than before treatment, the differences were statistically significance (P < 0.05), but there was no statistical significance in PIP, pH and Pplat before and after treatment (P > 0.05). The PaO2 of the observation group was higher than that of the control group, and the PaCO2, MAP, PEEP and PIP were lower than those of the control group, the differences were statistically significance (P < 0.05), but there was no statistical significance in PaO2/FiO2, pH and Pplat between the two groups (P > 0.05). The mechanical ventilation time, total oxygen inhalation time and hospital stay of the observation group were shorter than those of the control group, the differences were statistically significance (P < 0.05). The incidence of complications in the observation group was 10.00 %, which was consistent with that in the control group, there was no statistical significance (P > 0.05). Conclusion In the treatment of neonatal pneumonia with respiratory failure, the effect of using pulmonary surfactant under mechanical ventilation is more significant than that of mechanical ventilation alone.