A manufacturing technology applying a special spiral-fluted electrode in traditional ECM (Electro-chemical Machining) is introduced, this method is provided with the advantages of both narrow-gap ECM and pulsed current ECM. It is a new technological method for expanding holes in hard metal materials parts. In this paper, a new type ECM electrode is proposed to solve hole expanding problem in carbide drill bush. The machining principles and the influence of some operating parameters of ECM on the machining precision and productivity are described. Experiments results indicate that the accuracy and quality of the machined surface and the machining efficiency could be improved greatly by applying spiral-fluted electrode in ECM. It is also showed that the inner surface of the carbide bush was finished easily by this method with the optimal operating parameters, at the same time, the surface roughness of a machined hole is improved to 1ess than 0.2m Ra, and the dimensional accuracy of hole can reach 0.02mm.