Objective To investigate the distribution and antimicrobial resistance of pathogens in bronchoalveolar lavage fluid (BALF) of patients with lower respiratory tract infection ,and provide basis for rational choice of antimicrobial agents in clinic.Methods Retrospectively analyse the results and clinical data of quantitative isolation and culture of bacteria and antimicrobial resistance in bronchoalveolar lavage fluid of the First Affiliated Hospital of Nanjing Medical University during 2018. Results A total of 197 strains of pathogenic bacteria were isolated from 178 patients. 101 cases (56.7%) of community acquired pneumonia(CAP) and 77 cases (43.3%) of hospital acquired pneumonia(HAP) were mainly from intensive care unit (30.5%), geriatrics (29.5%) and respiratory and critical care medicine (26.4%).Gram-negative bacteria accounted for 89.5% of HAP patients and Gram-negative bacteria accounted for 77.5% of CAP patients, but the proportion was lower than that of HAP patients.Gram-negative bacteria accounted for 82.7%(163/197).The top three pathogens were Acinetobacter baumannii (34.1%,71/208), Pseudomonas aeruginosa (17.3%,36/208) and Klebsiella pneumoniae (14.0%,29/208)..Fungi accounted for 9.6%(21/197), including16 strains of Candida, 4 strains of Aspergillus and 1 strain of Malassezia furfur.Gram-positive bacteria accounted for 6.6%(13/197), mainly Staphylococcus aureus (5.0%,10/197).The resistance rates of Acinetobacter baumannii to imipenem and meropenem were 98.6%. The resistance rates of Pseudomonas aeruginosa to imipenem and meropenem were 29.4% and 23.5% respectively. The resistance rates of Klebsiella pneumoniae to imipenem and meropenem were 57.1%.Six methicillin-resistant Staphylococcus aureus (MRSA) strains were detected from 10 strains of Staphylococcus aureus with a detection rate of 60%.Staphylococcus aureus resistant to vancomycin and linezolid was not detected. Conclusion The common pathogenic bacteria in bronchoalveolar lavage fluid are Gram-negative bacteria, and the drug resistance of each pathogen is serious.n clinic, rational drug use should be strictly based on drug sensitivity results to reduce the incidence of pulmonary infection.