Objective：To study the phenotypic and genotypic distribution of Acinetobacter baumannii in Yizheng area to carbapenem drug resistance，and to explore the main mechanism of carbapenem resistance of Acinetobacter baumannii. Methods：The clinical isolates of Acinetobacter baumannii were divided into two groups according to the results of routine drug sensitivity test. Twenty-five strains of extensively drug-resistant Acinetobacter baumannii（XDRAb）and 23 of common strains were selected to detect metal β-lactamases by modified EDTA disk synergy method. Carbapenem was detected by carbapenem inactivation method，chromosome and plasmide-mediated AmpC enzyme were detected by double disk synergy test and modified three dimensional test，and the resistant genes blaOXA-23，blaOXA-24，blaTEM，blaAmpC，blaVIM，and blaNDM-1 were detected by PCR method，and some positive products were sequenced and compared. Results：The XDRAb group and the common group accounted for 62.5% and 37.5%，respectively. One strain of metal β-lactamase，4 strains of carbapenemase，and 1 strain of chromosome and 23 strains of plasmide-mediated AmpC enzyme were positive in the XDRAb group，but none of them were detected in the common group. The genes blaOXA-23，blaTEM，and blaAmpC were detected in all strains of XDRAb，and blaOXA-24，blaVIM，and blaNDM-1 were not detected in all of them. In the normal group，4 strains of blaOXA-23，5 strains of blaOXA-24，22 strains of blaTEM and 12 strains of blaAmpC were detected respectively，while blaVIM and blaNDM-1 were not detected in all strains. The difference of plasmid mediated AmpC enzyme，blaOXA - 23，and blaAmpC gene carrying rate between the two groups was statistically significant（χ2=40.627，34.183，15.511，P < 0.001，respectively）. The results of gene sequencing showed that the sequence of some strains was changed by base insertion or replacement. Conclusion：The drug resistance of Acinetobacter baumannii to carbapenem is serious in Yizheng area. The main mechanisms of Acinetobacter baumannii resistance to carbapenem are plasmide-mediated AmpC enzyme，blaOXA-23 and blaAmpC gene mediated drug resistance.