Abstract: Objective To provide the reference for the clinical control of Gram-negative bacteria lower respiratory tract infection（LRTI） by studying the characteristics of patients with Gram-negative bacteria LRTI,the distribution and drug resistance of Gram-negative bacteria in Respiratory Intensive Care Unit of our hospital,and analyzing the risk factors for the mortality of LRTI patients. Methods Clinical data about Gram-negative bacteria LRTI patients admitted to Respiratory Intensive Care Unit of our hospital from January 2009 to March 2010 and the possible risk factors for mortality of LRTI patients were retrospectively analyzed.Distribution of the bacteria in lower respiratory tract was investigated,and drug sensitivity test was performed fro the bacteria. Results APACHE-Ⅱ score was the risk factor for mortality of Gram-negative bacteria LRTI patients.One hundred and five strains of Gram-negative bacteria were isolated from 71 LRTI patients,of which Acinetobacter baumannii and Paeudomonas aeruginosa accounted for 60.9% and 27.7% respectively.Drug sensitivity test showed that the resistance of Acinetobacter baumannii to minocycline and other antibiotics was 81.3% and over 95% respectively,while that of Paeudomonas aeruginosa to a variety of antibiotics was over 55%. Conclusion The higher the APACHE-Ⅱ score is,the higher the mortality of LRTI patients is.The main Gram-negative bacteria found in LRTI patients of our department are Acinetobacter baumannii and Paeudomonas aeruginosa,thus drug sensitivity test should be routinely performed and antibiotics should be rationally used in clinical practice.