The effect of the W particle size and composition on the properties of Cu-W electrodes for electric discharge machining was surveyed. It was found that the smaller the W particle size and the lower the content of Copper in Cu-W alloy, the more excellent properties of Cu-W electrodes. It is considered that the size of Cu segregations in composite materials is dependent on the particle size of W powder and content of Cu and it changed the arc-discharge wear form.