ObjectiveTo survey and control an extensively drugresistant Acinetobacter baumannii(A. baumannii) (XDRAB) lower respiratory tract infection（LRTI） outbreak in intensive care unit (ICU) of a hospital. MethodsFrom October 27, 2013  to December 27, 2013， 5 cases of XDRAB LRTI occurred in ICU，epidemiological investigation was conducted， sources and transmission routes of infection were searched,  intervention measures were performed. ResultsXDRAB were isolated from patients’ sputum and environmental object surface, drugresistant spectrums of isolated XDRAB were almost the same， suggesting the outbreak was due to the contamination of environment by the same pathogen. 54 specimens were taken before disinfection,  26 were positive, XDRAB were isolated from door handles, sheets and telephones.  Investigation concluded that the outbreak of XDRAB infection was due to contamination of indoor environment and equipment， incomplete disinfection， and inadequate hand hygiene compliance of health care workers. After the implementation of a series of control measures, XDRAB was not found, and there was no new XDRAB infection cases. ConclusionEnvironment contamination is the main cause of this XDRAB healthcareassociated infection（HAI） outbreak, strict implementation of isolation,prevention and control measures of MDROs can effectively control HAI outbreak caused by A. baumannii.