OBJECTIVE To review the alteration of distribution of familiar Gram-negative bacteria of lower respiratory tract infection for patients in intensive care unit(ICU) of our hospital for reference to rational administration of clinical antibacterial drug.METHODS The 476 strains out of 736 strains collected from patients of our hospital during Jan 2003 to Dec 2006 were Gram-negative bacteria,positive ratio was 64.67%,and the features of distribution and alteration were statistically summarized.RESULTS The main germs of the 476 strains were Acinetobacter baumannii(102 strains),Pseudomonas aeruginosa(94 strains),Klebsiella pneumoniae(66 strains),Escherichia coli(54 strains),and Stenotrophomonas maltophilia(33 strains).CONCLUSIONS The main germs of pathogenic germs of lower respiratory tract infection for patients in ICU are Gram-negative bacteria,among which the isolation ratio of A.baumannii is the highest.But S.maltophilia is increasing gradually,indicating that clinical doctor should watch alteration of Gram-negative bacteria,and rationally use antibacterial drug in order to raise cure rate.