ObjectiveTo investigate antimicrobial resistance of Acinetobacter baumannii (A. baumannii)  causing hospitalacquired pneumonia (HAP)， so as to guide rational use of antimicrobial agents and reduce antimicrobial resistant rate.MethodsClinical data of patients with A. baumannii HAP in a hospital between 2009 and 2012 were collected and analyzed retrospectively. Antimicrobial resistance data were summarized and analyzed statistically according to uniformed methods.ResultsA total of 284 patients developed A.baumannii HAP， patients mainly distributed in intensive care unit（45.07%）,  department of respiratory diseases（19.01%）, neurosurgery （9.15%）, and  neurology（5.99%）. The incidences of A. baumannii  HAP，multidrugresistant A. baumannii (MDRAB) HAP， and extensively drugresistant A. baumannii (XDRAB) HAP increased year by year.  The total resistant rates of A. baumannii to cefoperazone/sulbactam (9.51%) and minocycline(9.86%) were low,  to levofloxacin(43.66%) and ciprofloxacin(45.42%) were relatively higher; resistant rates to imipenem and  meropenem were 16.20% and 20.42% respectively. The resistant rates to meropenem, imipenem, cefoperazone/sulbactam,  and ampicillin/sulbactam increased year by year (all P<0.05).ConclusionAntimicrobial resistance of A. baumannii is serious, it is essential to strengthen the monitoring of antimicrobial resistance of A.baumannii, and  prevent the spread in hospital.