A novelty technique,namely,pre-oxidation,has been proposed to improve the strength and thermal shock behavior of ZrB2-SiC-graphite ceramic composites,which is a promising candidate for ultra-high temperature ceramics (UHTCs) in aerospace engineering.The composite is pre-oxidized at temperatures of 900 ℃ and 1100 ℃ for 1 h and 3 h in air.A theoretical model considering surface heat transfer has been given and analyzed.A water-quenching technique is adopted at different temperatures from 300 ℃ to 600 ℃ in order to investigate the thermal shock behavior of pre-oxidized composites.The critical thermal shock temperature improves more than 40％ after pre-oxidizing at 1100 ℃ for 3 h.However,the composites strength is not improved as a result of the insensitivitv to surface defects.