A surface plasmon resonance biosensor based on ZnO-Au nanocomposites was developed for the detection of rabbit IgG. The ZnO-Au nanocomposites can bind protein by covalent attachment to construct a probe for target analyte. The probe with unique optical properties and good biocompatibility could enhance the sensitivity of SPR biosensor. Under the optimized conditions, the biosensor based on ZnO-Au nanocomposites exhibits a satisfactory response to rabbit IgG in the concentration range of 0.15-20.00 mu g ml(-1). For comparison, the biosensor based on Au film and the biosensor based on Au nanoparticles were also studied for the detection of rabbit IgG. The biosensor based on Au film shows a response to rabbit IgG in the concentration range of 2.50-20.00 mu g ml(-1). The biosensor based on Au nanoparticles shows a response in the concentration range of 0.30-20.00 mu g ml(-1). The biosensor based on ZnO-Au nanocomposites was therefore found to be the most sensitive of the three types of biosensors. The lowest concentration of rabbit IgG that can be determined by the proposed biosensor is about 16-fold lower than that of the biosensor based on Au film alone. (C) 2010 Elsevier Inc. All rights reserved.