ZrB2-10 vol.% SiC ceramics were hot pressed with addition of two contents of ZrO2, i.e., 10 vol.% and 20 vol.%. Oxidation behavior of ZrB2-SiC-ZrO2 ceramics was investigated using muffle furnace in the temperature range of 800-1200 degrees C in air. With the increase in temperature and extension in holding time, two ceramics both presented more and more severe oxidation behavior. Comparatively, results of microstructure indicated that ceramic with 10 vol.% ZrO2 always exhibited lighter variation in structure after oxidation. Further discussion showed that ceramic with 10 vol.% ZrO2 also provided lower mass gain and thinner oxidized layer. Analysis of oxidation mechanism revealed that excessive addition of ZrO2 brought much path to the inward transport of oxygen and therefore led to the serious oxidation for ZrB2-SiC-ZrO2 ceramics. (C) 2009 Elsevier B.V. All rights reserved.