Abstract: Objective：To investigate the molecular prevalent feature of imipenemresistant Acinetobacter baumannii (IRAB) in our hospital, and analyze its molecular mechanism of resistance to carbapenems. Methods：Fifty-four nonrepetitive IRAB strains isolated from different clinical departments were collected from November 2009 to January 2010. The antimicrobial susceptibility test was performed with Vitek2 Compact system. The homology of IRAB was analyzed by pulsed field gel electrophoresis (PFGE). The related resistance genetypes of carbapenemase and 16S rRNA methylase were detected by PCR and DNA sequencing. Results：Fifty-four IRAB strains were distributed into type A and B according to PFGE results. Among the 54 strains, 42 strains (77.8%) belonged to type A which was the main prevalent type and distributed in all the departments, and 10 strains (18.5%) belonged to type B which only distributed in the intensive care units (ICU) of neurology and neurosurgery departments. OXA-66 gene was carried by all the 54 strains, OXA-23 gene and its upstream insertion sequence ISAba1 was carried by 53 stains, and the armA gene of 16S rRNA methylase was carried by 41 strains. Conclusion：Type A of IRAB was disseminated widely in the clinical departments of our hospital, while type B spread in ICU of neurology and neurosurgery departments. The existence of OXA-23 gene and its upstream insertion sequence ISAba1 was the main cause leading IRAB to resist carbapenems. 16S rRNA methylase armA gene was widely distributed in IRAB strains.