Abstract： Objective To study the expression of active efflux pump AdeABC,AdeIJK,AdeFGH,AbeM,AbeS,CraA,MdtL in clinical Acinetobacter baumannii isolates and whether the efflux pumps confers resistance to antibiotics.Methods Thirty-two multi-drug resistant Acinetobacter baumannii islates and 10 sensitive isolates were collected.Genes of the exporter protein were amplified by PCR.The expression of adeB,adeJ,adeG,abeM,abeS,craA,mdtL were examined by real-time fluorescence quantitative RT-PCR.The controlling genes adeRS and adeL were amplified by PCR and sequenced.Results The positivity rates of adeB,adeJ,adeG,abeM,abeS,craA,mdtL were 100％,100％,100％,96.88％,100％,100％ and 93.75％ respectively in 32 multi-drug resistant Acinetobacter baumannii isolates,and all 100％ in 10 sensitive isolates.The difference of expression of adeB,abeM and mdtL were significant( P＜0.001,P =0.001,P=0.013) between 21 multi-drug resistant isolates of C clone and 10 sensitive isolates.The mutations of adeRS existed in 2 multi-drug resistant isolates,no point mutation of adeL.Conclusion The expression of AdeABC,AbeM and MdtL may involved in the resistant mechanisms of the clinical Acinetobacter baumannii islates.