ObjectiveTo investigate the distribution and antimicrobial resistance of pathogens causing lower respiratory tract (LRT) infection in an intensive care unit(ICU), and provide reference for empiric therapy.Methods2 613 pathogenic strains isolated from LRT of patients in an ICU in 2011-2015 were performed statistic and antimicrobial susceptibility analysis.ResultsOf 2 613 strains, 2 308（88.33％) were gramnegative bacteria，236(9.03％) were grampositive bacteria, and 69(2.64％) were fungi. The top 5 pathogens were Acinetobacter baumannii, Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus aureus, and Serratia marcescens, accounting for 33.64%，16.42%，15.19%，7.35%, and 4.90% respectively. Resistance rates of Acinetobacter baumannii to most antimicrobial agents were＞75.00%，resistance rate to imipenem was 80.32%；resistance rates of Pseudomonas aeruginosa, Klebsiella pneumoniae, and Serratia marcescens to imipenem were 16.08%-34.38%, to amikacin, cefepime, and piperacillin/ tazobactam were all＜30.00％. Susceptibility of grampositive bacteria to vancomycin and linezolid were both 100.00%. Resistance rates of Staphylococcus aureus and Staphylococcus heamolyticus to oxacillin were 81.77% and 100.00% respectively.ConclusionGramnegative bacteria are the main pathogens isolated from LRT in ICU patients, and nonfermentative bacteria ranked the first. Antimicrobial resistance are serious for most pathogens, antimicrobial agents should be chosen rationally according to antimicrobial susceptibility testing results.