ZrB2-SiC ultra-high temperature ceramic composites reinforced by nano-SiC whiskers and SiC particles were prepared by microwave sintering at 1850°C. XRD and SEM techniques were used to characterize the sintered samples. It was found that microwave sintering can promote the densification of the composites at lower temperatures. The addition of SiC also improved the densification of ZrB2-SiC composites and almost fully dense ZrB2-SiC composites were obtained when the amount of SiC increased up to 30vol.%. Flexural strength and fracture toughness of the ZrB2-SiC composites were also enhanced; the maximum strength and toughness reached 625？MPa and 7.18？MPa·m1/2, respectively.
