Particulate ceramic composites composed of Si3N4 matrix and dispersing TiN particles were sintered in N2 atmosphere at 1850℃ for 1h. The physical and mechanical properties of these composites containing 10, 20, 30 and 40vol% TiN were evaluated. The microstructure, strength, fracture toughness and electrical resistivity of Si3N4 containing two different sizes of TiN were investigated. The size and content of TiN particles were found having effects on the strength, toughness and electrical resistivity of TiN/Si2N4 composites. A low electrical resistivity of 3×10^(-3)Ω.cm was obtained in 40vol% TiN/Si3N4 composites and it was suggested that this composite would be appropriate for the machining of EDM. The results demonstrated the possibility of machining structural ceramics by the micro-EDM method through the incorporation of conductive toughening phases.