The SiCN/ZrB 2 ceramic composite was prepared from a liquid polyvinylsilazane with addition of ZrB 2 powders, subsequently crosslinked at 300°C and pyrolysed at 1000°C in flowing Ar. Scanning electron microscopy (SEM) and X-ray diffractometry (XRD) showed that SiCN/ZrB 2 consists of dense amorphous SiCN matrix with dispersed micron ZrB 2 crystals. Thermal gravimetric analysis (TGA) showed SiCN/ZrB 2 was stable up to 1550°C in Ar with 5.4% weight loss, 6.4% lower than the pure SiCN ceramic. Heat treatment from 1100°C to 1500°C was performed to initiate crystallization. XRD showed thata SiCN matrix of SiCN/ZrB 2 remained amorphous up to 1400°C in Ar and indicated new crystals formed such as ZrO 2 at 1100°C, ZrC/ZrN at 1200°C and Zr 2 CN at 1500°C, which account for the improved high-temperature stability of the material.