In this study, the paper introduces the surface roughness results of heat-treatment, and unheated-treatment SKD61 steel was processed by the EDM method with the participation of tungsten carbide powder. The least-square method was used to model the relationship between surface roughness of heat-treatment and unheated-treatment SKD61 steels, and these models were used to evaluate the role of each technological parameter, comparing the role of each technological parameter in the two models