Abstract: TiB-TiB<sub<2</sub< ceramic composites are in situ synthesized by spark plasma sintering technique under a pressure of 50MPa, with sintering temperature ranging from 800℃ to 1700℃ and a heating rate of 150℃/min, using Ti and TiB<sub<2</sub< powders. Microstructures and mechanical properties of the composites sintered at different temperatures were investigated. According to the microstructure evolution of the composites, the description of the sintering process can be divided into 3 stages: splashing of metal Ti under the discharge effect, reaction of the molten Ti with TiB<sub<2</sub<, and rapid densification of the composites due to the rapid solid-state diffusion and large plastic deformation result from the Joule heating effect and pressure loading effect.