The oxidation behavior of ZrB2-20 vol.% SiC (ZS) and ZrB2-20 vol.% SiC containing 20 vol.% short carbon fiber (ZSC) was studied using thermal gravimetric analysis and oxyacetylene torch test. It was shown that weight gains changed from 3.71 wt.% for ZS to 4.57 wt.% for ZSC after heating 10°C /min to 1450°C in air. A thin layer of Si-rich glass and then a depletion layer of SiC was found on the cross section of both materials and carbon fiber of ZSC exposed in air was oxidized. Under oxyacetylene, an average mass loss of 0.8 wt.% for ZS and 0.9 wt.% for ZSC was measured after 180 seconds. After exposure, an oxidized layer with the formation of ZrO2 and SiO2 was found on the surface of both materials. Meanwhile, fiber in the surface of ZSC appeared oxidized and removed.