Electroconductive TiN/O′-Sialon multiphase ceramics were prepared by pressureless sintering from TiN/O′-Sialon powders as the chief raw material which were synthesized by the carbothermal reduction nitridation method using high titania slag, silicon fume and bauxite chalmette. Phase compositions and were analyzed. The effect of microstructure and TiO2 content in initial raw materials on electrical conductivity were studied by SEM and TEM. The electro-discharge machining (EDM) of the materials was carried out. The results show that the sintered samples consist of O′-Sialon and TiN. O′-Sialon grains exhibit equiaxied morphology and the particle sizes are about 1-3μm. TiN grains exhibit fine granular morphology and most of grains have lower size than 0.5μm. The minimum amount of TiO2 in initial raw materials is 25wt% for the formation of electroconductive network in the multiphase ceramics, of which the electrical resistivity is 1.8×10-2 Ω·cm and meets the requirement of electrical discharge machining.