Objective To investigate the causes for the continuous detection of Pseudomonas fluorescens (P. fluorescens) from bronchoalveolar lavage fluid (BALF) in pediatric department of a hospital, formulate intervention measures and evaluate its effectiveness, and provide basis for improving the whole process infection control of fiber bronchoscopy. Methods Epidemiological investigation was conducted on three children from whose BALF P. fluorescens were detected in May 3-6, 2024. The comprehensive methods were adopted, including case reviewing, on-site process tracking, environmental hygiene monitoring, laboratory testing on disinfectant sterilization effect, fiber bronchoscope structure maintenance and checking, etc. Risks were identified and targeted interventions were implemented. Results Among the 5 pediatric patients who underwent fiber bronchoscopy within 4 days, P. fluorescens was detected from BALF of 3 cases, with a detection rate of 60.0%. The children were 5-8 years old and were admitted to the hospital due to lobar pneumonia. They underwent fiber bronchoscopy from the day of admission to the second day, and bacterial strains were clinically determined to be contaminated strains. Environmental sampling showed that the detection rate of P. fluorescens at sampling points such as fiber bronchoscope and enzyme solution storage tank was 15.7% (8/51). After implementing intervention, no target bacteria were detected again, and the difference was statistically significant (P<0.05). From January 1 to May 2, 2024, 71 BALF from pediatric department were not detected P. fluorescens; From May 3 to 6, among 5 detected BALF, 3 were detected P. fluorescens; After intervention (May 16 to December 31), no specimen was detected P. fluorescens. Conclusion This event is a pseudo-outbreak caused by fiber bronchoscope damage as well as improper cleaning and disinfection procedures. Through collaborative investigation and timely intervention by multiple departments, the event was effectively controlled.