ObjectiveTo analyze the epidemiological characteristics of a healthcareassociated infection(HAI) outbreak due to multidrugresistant Acinetobacter baumannii (AB) in an intensive care unit(ICU), and provide basis for the prevention and control of HAI. MethodsEpidemiological investigation and environmental hygiene monitoring methods were adopted to investigate patients who had pulmonary infection after they were admitted to the ICU of a hospital in April 126, 2015, risk factors were analyzed and corresponding preventive control measures were taken.Results A total of 15 cases of extensively drugresistant AB(XDRAB) healthcareassociated lower respiratory tract infection occurred. 15 strains of AB were isolated from 15 patients. No. 1, 3, 4, 5, No. 6, 7, 8, 9, and No. 10, 11 patients were detected AB with the same antimicrobial susceptibility testing results respectively; occurrence time of infection was relatively centralized. A total of 43 specimens from environmental surface and hands of health care workers(HCWs) were collected, detection rates of AB from bedside cabinet, monitor button, and hands of HCWs were 100.00%(1/1), 75.00%（6/8）, and 66.67%（4/6）respectively. AB were not detected from specimens of treatment table, infusion pump button, and doctors’ nasal swabs. By late May 2015, there were no new such cases in ICU. ConclusionThis AB HAI may be spread through environmental surface and hands of HCWs in ICU, AB isolated from patients is extensively antimicrobial resistant, active treatment of patients and strict disinfection and isolation measures can effectively control further prevalence.