Objective:To explore the molecular epidemiology character of carbapenem-resistant Acinetobacter baumannii (CRAb) by phenotyping and genotyping methods,and provide evidence of molecular epidemiology to prevent nosocomial infection(NI). Methods: In this study,40 CRAb strains were isolated from patients of intensive care unit(ICU). Broth dilution method were used to detect patterns of resistant against 14 antimircobial agents,and multiplex PCR was performed to detected class D β-lactamase encoding genes. Phenotype of metallo-β-lactamase were detected by EDTA disk method,blaIMP,blaVIM,blaSIM amplified by PCR method. Pulsed-field gel electrophoresis(PFGE) was analyzed to find the relationship among these isolates. Results: All CRAb kept low susceptibility to amikacin, gentamicin and levofloxacin, but resistance to other agents. All CRAb producing carbapenemases were confirmed as OXA-23 by PCR and sequencing. A promoter ISAba1 was found in the upstream of OXA-23. Metallo-β-lactamase was negative in any of the isolates. They were classified into 4 clones based on PFGE pattern. Clone A and D had been spreading widely. In all 40 infection patients,34(85.0%) were respiratory tract infections,5(12.5%) were wound infection,1(2.5%) were bloodstream infections. After clinical treatment,21 (52.5%) survived,12 (30.0%) died,and 7 were not discharged. Conclusion: All CRAb caused outbreak producing OXA-23 carbapenemase,and the main genetypes included clone A and clone D. And with the role of antimicrobial drug-selective pressure,full-resistant strains have appeared.