Abstract: Objective To evaluate the combined in vitro inhibitory effect of cefoperazone/sulbactam（CFS）,rifampicin（RFP）,minocycline（MIN） and levofloxacin（LEV） on clinically isolated carbapenem-resistant acinetobacter Baumannii（CRAB） strains. Methods Combined in vitro inhibitory effect of CFS,RFP,MIN and LEV was assayed by detecting the maximal inhibitory concentration and calculating the fractional inhibitory concentration（FIC）index for 60 CRAB strains with the micro-broth dilution method. Results Combined CFS and RFP showed 80% synergic effect,16.7% additive effect,3.3% indifferent effect and no antagonistic effect on CRAB strains.Combined CFS and MIN displayed 11.7% synergic effect,45% additive effect,35% indifferent effect and 8.3% antagonistic effect on CRAB strains.Combined CFS and LEV demonstrated 6.7% synergic effect,40% additive effect,53.3% indifferent effect and no antagonistic effect on CRAB strains.The MIC50 of these drugs was significantly lower when they were used in combination with their concentration-accumulative curves shifted to the left. Conclusion Combined CFS,RFP and MIN shows a combined in vitro synergic and additive inhibitory effect on CRAB strains.Combined CFS and LEV displays an indifferent effect on CRAB strains,and a synergic and additive effect on nearly 50% CRAB strains.