Objective To explore the presence of resistance genes in Acinetobacter baumannii which showed doublecircle resistant to aminoglycoside antibiotic by detection with KB methods, and analyze the expression levels of resistance gene mRNA among the strains induced and noninduced by amikacin. Methods A total of 42 strains of class I integronpositive Acinetobacter baumannii was collected, and the variable region was analyzed by PCR and RFLP. DNA sequencing was used to identify the gene cassettes of variable integrons. The genes expressions in druginduced and noninduced strains were measured by PT-PCR respectively. Results Of the integronpositive strains 90.4% (38/42) contained variable region, and the size of the amplicons was about 2 300 bp. The results of RFLP and DNA sequencing showed that the cassettes carried in the variable region of integrons were aacA4-catB-aadA1. PT-PCR revealed that the expression level of aacA4 gene mRNA was significantly upregulated when the strains were induced by amikacin. Conclusion The integrons class I in doublecircle strains may mainly carry the genes resistant to aminoglycoside. The phenomenon of doublecircle may associate with the inducible expressed genes.