Room-temperature electrical conductivity property of Si3N4/TiN composite ceramics fabricated by Si3N4 powders from iron ore tailing and high titanium slag was investigated. Si3N4/TiN composite ceramics were machined by electrical discharge machining. The results show that the minimum amount of TiO2 in initial raw materials is about 20wt% for the formation of electroconductive network in the composites, of which the electric resistivity is 4.25×10-2•cm. The electric resistivity decreases slightly with increasing the sintering temperature. Surface roughness enhances significantly with the speed of the electrical discharge machining rising.