In this paper, a study on multi-objective optimization when powder-mixing discharge machining (PMEDM) of cylindrical parts made of SKD11 steel is conducted to achieve the minimum surface roughness (SR) and the speed minimum electrode wear rate (EWR). To solve this problem, an experiment was conducted with the use of the Taguchi method for design and the gray relational analysis (GRA) method to analyze the results. In addition, six input parameters including powder concentration, powder size, pulse generation time, pulse off time, servo current and voltage were taken to study their effect on SR and EWR. Moreover, optimal input parameters to achieve the minimum SR and minimum EWR simultaneously have been proposed.