Objective The aim of this study was to investigate the efficacy and safety of bronchoalveolar lavage (BAL) in the treatment of neonatal severe pneumonia (NSP). Methods One hundred patients with severe pneumonia were randomly divided into two groups, the BAL and control groups, with 50 patients in each group. In the BAL group, normal saline was instilled into the endotracheal tube for BAL. Before and after lavage, lung ultrasound (LUS) monitoring was performed to observe the lung pathological changes. Conventional treatment was administered in the control group. The need for and duration of invasive mechanical ventilation, the complication rate, the duration and cost of hospitalization and the mortality rate were compared between the two groups. Results The results of this study showed that there were 35 (70%) patients who meet the indications of the invasive mechanical ventilation (IMV) at admission in the BAL group, while there were only 15 (30%) patients still requiring IMV after BAL therapy. The duration of IMV was 41.7 ± 7.5 vs. 97.7 ± 12.9 h in BAL and controls, the incidence rate of complications was 8.0% vs. 20.0% in both groups, the length of hospital stay was 9.2 ± 1.9 vs. 14.1 ± 2.1 days in both groups, and the expense of hospital cost was 12 557 ± 832 vs. 19 121 ± 929 Chinese Yuan in both groups. All patients had stable vital signs during lavage, and no significant adverse side effects were observed. Conclusion BAL was significantly beneficial for NSP with no significant adverse side effects; LUS is a useful tool for the timely detection of BAL effects.