This paper presents the results of an optimization study on powder-mixed electrical discharge machining (PMEDM) when machining cylindrical parts made of SKD11 tool steel. The objective of this study was to investigate the influence of main process parameters on the ratio of the surface roughness (SR) to the material removal speed (MRS). To do that, an experiment was conducted. Also, the Taguchi method in Minitab 19 software was used to design and analyze the experimental results. The influence of the input process parameters, including the powder concentration, the powder size, the pulse on time, the pulse off time, the servo current, and the servo voltage on the ratio between SR and MRS was evaluated. Furthermore, the optimal input parameters to achieve the minimum ratio of SR to MRS were found.