Acinetobacter baumannii readily developed antimicrobial resistance to clinically available antibiotics. A. baumannii DU202 is a multi-drug resistant strain, and is highly resistant to tetracycline (MIC>1,024 micro/ml). The surface proteome of A. baumannii DU202 in response to the sub-minimal inhibitory concentration (subMIC) of tetracycline was analyzed by 2-DE/MS-MS and 1-DE/LC/MS-MS to understand the pathways that form barriers for tetracycline. Membrane expression of major outer membrane proteins (Omps) was significantly decreased in response to the subMIC of tetracycline. These Omps with sizes of 38, 32, 28, and 21 kDa were identified as OmpA38, OmpA32, CarO, and OmpW, respectively. However, transcription level of these Omps was not significantly changed. 1-DE/LC/MS-MS analysis of secreted proteins showed that OmpA38, CarO, OmpW, and other Omps were increasingly secreted at tetracycline condition. This result suggests that A. baumannii actively regulates the membrane expression and the secretion of Omps to overcome antibiotic stress condition.