Multidrug-resistant Acinetobacter baumannii is an important bacterium causing nosocomial infections; A. baumannii infections have increased in our hospital since 2009. However, multidrug-resistant A. baumannii, which was mainly isolated from patients in each intensive care unit (ICU), rapidly increased from December 2012 to January 2013. Therefore, we described the molecular characteristics of A. baumannii by pulsed-field gel electrophoresis (PFGE). We also detected resistance genes for β-lactam, aminoglycosides, and plasmid-mediated quinolones. Disinfectant-resistant genes were also detected in the clinical isolates of blaOXA-51-positive multidrug-resistant A. baumannii. The conjugative test was performed to detect whether or not resistance genes can be transferred to different strains. Carbonyl cyanide m-chlorophenylhydrazone (CCCP) inhibition test was conducted to analyze the factors influencing the resistance of A. baumannii to imipenem, meropenem, ceftazidime, levofloxacin, and tigecycline. PFGE profiles contained 12 strains, including 20 type C strains (47.6%), 4 type D strains (9.5%), and 1 to 3 strains of other types; 38 strains were distributed in patients in each ICU. In our test samples, the presence of blaOXA-23 was closely related to carbapenem resistance. The 16S rRNA methylase gene armA was associated with resistance to amikacin, gentamicin, and tobramycin. The multidrug-resistant A. baumannii was closely related to various resistance genes. These results indicated that multidrug-resistant A. baumannii with type C strains was predominant in our hospital in this period.