ObjectiveTo investigate the risk factors for hospitalacquired lower respiratory tract infection（LRTI）in an intensive care unit (ICU) , so as to provide reference for making effective measures for controlling healthcareassociated infection(HAI).MethodsA retrospective analysis was conducted on medical records of 1 062 ICU patients who were admitted in ICU from December 2008 to December 2010, patients’ hopitalization time was >48 hours, ages were ≥18 years old, 68 patients who were confirmed LRTI was as case group; by 1:2 matched cases of same gender, same age group, and same admission time, 136 patients without HAI was as control group, risk factors for LRTI were analysed.ResultsUnivariate analysis showed that length of stay in ICU≥15 days , incision of trachea, endotracheal intubation/mechanical ventilation,use of antimicrobial agents >2 types and duration >2 weeks, aerosol inhalation were risk factors of LRTI in ICU patients; Multivariate Logistic regression analysis on 9 screened risk factors showed that length of stay in ICU ≥15 days (OR 95% CI, 1.153-4.912), incision of trachea (OR 95% CI, 1.836-9.967), endotracheal intubation/mechanical ventilation (OR 95% CI,1.163-5.774), use of antimicrobial agents >2 types and duration >2 weeks (OR 95% CI,1.016-5.813) were independent risk factors for LRTI.ConclusionMultiple factors contribute to the occurrence of LRTI in ICU patients,comprehensive preventive treatment based on the risk factors is helpful for reducing HAI.