Objective:To investigate the etiology and antimicrobial resistance of predominant pathogen of ventilatorassociated pneumonia (VAP) isolated from intensive care unit. Methods:The bacteria isolated from sputum specimen and antimicrobial resistance of patients with VAP admitted between January 2003 and December 2006 in the Department of Intensive Care Unit of the First Affiliated Hospital of China Medical University were analyzed retrospectively. Results:During the period, the incidence of VAP in ICU was 191%.Pseudomonas aeruginosa，Burkholderia cepacia,Acinetobacter baumannii and Stenotrophomonas maltophilia were the most frequently isolated bacteria of VAP.Staphylococcus aureus increased steadily from 2003 to 2005 and then decreased in 2006.The total number of isolated Chryseobacterium meningosepticum decreased in 2005-2006.While the number of Klebsiella pneumoniae increased in 2005-2006.The resistance rate of Pseudomonas aeruginosa to antibiotics increased progressively in 2004 (above 75%) and to imipenem exceeded 40% during 4 years.Acinetobacter baumannii was less resistant to imipenem and levofloxacin.The resistance of Stenotrophomonas maltophilia to compound sulfamethoxazole,ciprofloxacin and levofloxacin was the lowest.Methicillinresistant Staphylococcus aureus composed the biggest part of all isolated Staphylococcus aureus. Conclusion:The main pathogens of VAP in ICU are nonfermenting gramnegative bacilli.The predominant pathogens are Pseudomonas aeruginosa,Burkholderia cepacia,Acinetobacter baumannii and Stenotrophomonas maltophilia.The pathogens distribution and infection spectrum have changed during 4 yeas.