In this paper, the effect of dielectric suspended with electrically non-conductive powder, such as alumina, on electrical discharge machining characteristics of SKD11 is investigated. The main results indicate that the alumina powder has no effect on the gap distance, but it is verified that the dielectric suspended with alumina powder has a significant influence on the electric discharge machining characteristics of SKD11. It was found also that the improvement mechanism of work surface finish due to the improved effect of the electrode surface and the recasting rise was restrained by the alumina particles. It was found also that it is an effective method for promoting the material removal rate of SKD11 when rotating the electrode and machining in the dielectric suspended with alumina powder under optimun conditions. The experimental results also indicate that the best performance from the viewpoint of surface finish is achieved using the conditions of the particles diameter of 1 μm, concentration of 4 g/L, and the electrode rotation speed of 60 rpm.