Abstract: Objective: To investigate the prevalence of β-lactamase genes and active efflux pump genes in Acinetobacter baumannii (A. baumannii) isolated from sputum samples of the patients with pneumonia. Methods: A total of 160 strains of A. calcoaceticus-A. baumannii complexes identified by routine biochemical methods and double PCR using A. baumannii specific fragment in internal transcribed spacer (ITS) sequence were collected. The β-lactamase genes and active efflux pump genes in these strains, including class A β-lactamase genes such as bla_TEM, bla_PER and bla_CARB, class B β-lactamase genes such as bla_IMP and bla_VIM, class C β-lactamases genes such as bla_ADC and bla_DHA, class D β-lactamases genes such as bla_OXA-23, bla_OXA-24, bla_OXA-51 and bla_OXA-58 and active efflux pump related genes such as adeB, adeJ, macB, emrB, emrA, abeS, abeM, and craA, were detected by PCR. The minimal inhibitory concentrations (MIC) of imipenem to A. baumannii with adeB gene were measured by the micro-broth dilution method before and after the treatment with the efflux pump inhibitor of carbonyl cyanide chlorpheniramine (CCCP). Results: A total of 143 strains of A. baumannii (143/160, 90%) were isolated from the A. calcoaceticus-A. baumannii complexes. Among them, 119 strains (83.2%) were resistant to imipenem, and the other 24 strains (16.8%) sensitive to imipenem. The bla_OXA-51 gene was detected in all of A. baumannii strains, and bla_OXA-23, bla_TEM, bla_ADC and bla_DHA genes were detected in 98.3%, 41.4%, 98.3% and 0.7% of imipenem-resistant strains, respectively. The bla_PER, bla_CARB, bla_IMP, bla_VIM, bla_OXA-24 and bla_OXA-58 genes were not found. However, the bla_OXA-23 gene was not found in imipenem-sensitive strains. All of 143 strains of A. baumannii carried adeJ, macB, abeM and craA genes, and more than 80% of strains carried emrB, emrA and abeS genes. The adeB gene was detected in 98.3% (117/119) of imipenem-resistant strains. After treated with CCCP, the MIC₅₀ of imipenem to A. baumannii with adeB gene was reduced by 1/2. Conclusion: A. baumannii carries bla_OXA-23 and adeB genes, which may be closely related to imipenem resistance.