C-W2B5 composites with a W2B5 content ranging from 30 to 60 vol.% at an interval of 10 vol.% were prepared by reaction hot-pressing sintering. Isothermal oxidation behavior of these materials at the temperature range from 700 to 1000 degrees C in air for 20 h was investigated. The results revealed that all the materials had better oxidation resistance than pure graphite. The oxidation activated energies of the composites increased from 108 to 262 kJ mol(-1) with W2B5 content increasing, which was attributed to the formation of a dense and continuous oxide layer of WO3 and B2O3 on the oxidation surface. The composition and morphologies of the oxidation surface and cross-section of the oxide layer were observed by XRD and SEM together with EDX. A general oxidation mechanism of the C-W2B5 composite was proposed. (c) 2006 Elsevier B.V. All rights reserved.