Abstract: The mechanism of chemical reaction and microstructure formation process of B₂O₃-TiO₂-Mg-C system were investigated in this paper. The results showed that TiB₂-TiC ceramic powder could be obtained by SHS from B₂O₃-TiO₂-Mg-C system. The results of analysis of different thermal analysis (DTA) and X-ray diffraction (XRD) showed the following thermal processes of B₂O₃-TiO₂-Mg-C system: B₂O₃ was reduced to B and TiO₂ was reduced to Ti. Metal Mg was melted at 650℃. At 680 ℃ the reaction between B and Ti nearly finished and the formation of TiC from the reaction of Ti and C began. TiO₂ was reduced to element Ti step by step through the following way: TiO₂→TiO→Ti. TiB₂-TiC composite powder with particle size of 45 percent under 1μm and 87 percent under 3μm was obtained after MgO, the unwanted phase, was removed by leaching in hydrochloric acid. Results of SEM micrographs of TiB₂-TiC ceramic multiphase powder showed that the particle size is much smaller than that of single phase TiB₂ or TiC produced by the same methods. The mole ratio of Ti and C in TiC was 1∶0.7483.