Abstract: This study analyzes the causes of two cases of hospital-associated pulmonary infection caused by Pseudomonas aeruginosa in the neonatology department of a three-A hospital in Sept. 2023, as well as the effects of intervention measures for improvement. An epidemiological investigation was conducted to trace the source of the two cases of hospital-associated pulmonary infection caused by P. aeruginosa in the neonatology department. Environmental hygiene sampling was performed on potentially contaminated environmental surfaces, hands, medical supplies, sinks and water sources to deduce the transmission routes and sources of the P. aeruginosa infection: the sink of the neonatology department was contaminated with P. aeruginosa, which subsequently contaminated the medical equipment placed next to the sink and the hands of medical staff. Through medical procedures such as suctioning and nursing care, two children were infected in a cluster manner. After taking a series of intervention and treatment measures, no additional cases of cross-infection occurred in the hospital, and the hospital-associated infection outbreak was contained in its early stage.