ZrB2-SiC-BN ultrahigh-temperature ceramic (UHTC) was fabricated by hot-pressing at 1800°C under 23MPa pressure of argon. Compared to ZrB2-SiC, the flexural strength of ZrB2-SiC-BN composite material was enhanced by adding 30% BN, and the fracture toughness showed a slight decrease, while the hardness decreased sharply. The addition of 30% BN also noticeably improved the machinability of the composites. Furthermore, ablation resistance tests were carried out using an oxyacetylene torch under subsonic conditions. Results indicated that a coherent compact scale of zirconium silicate was formed, which acted as an effective barrier against the inward diffusion of oxygen.