ObjectiveTo investigate the sources and transmission routes of clustered cases of healthcareassociated infection（HAI） caused by multidrugresistant Acinetobacter baumannii (MDRAB) in the intensive care unit (ICU) of a hospital, and provide evidence for the prevention and control of HAI.MethodsClustered cases of MDRAB HAI in ICU were investigated, specimens of patients and environment were collected and cultured, the isolated strains were performed antimicrobial susceptibility testing.ResultsFive strains of pathogenic bacteria were isolated from sputum of patients with HAI, 5 infected patients were at adjacent beds from the same ICU; the onset time was on January 2-7, 2016. A total of 21 strains of pathogenic bacteria were isolated from environmental specimens during the same period, these strains were from quilt, bedside cabinet, treatment trolley, faucet, bedrail, breathing tube, and hands of health care worker(HCWs). Antimicrobial susceptibility testing results showed that strains from patients and environment were all MDRAB, and had the similar antimicrobial resistance pattern.ConclusionThe occurrence of clustered HAI cases is due to contamination of HCWs’ hands and hospital environment by MDRAB.