The present paper presents a study of the optimum selection of wire electric discharge machining conditions for CK45 steel. Response surface methodology (RSM) has been utilized to analyze and determine the optimal parameters setting in the WEDM for CK45 steel. The process performance criteria such as material removal rate, tool wear rate, and surface roughness were evaluated. Feeding speed, duty factor, water pressure, wire tension and wire speed, have been considered the main factors affecting WEDM performance. RSM was employed for developing experimental models. Analysis of variance test has also been carried out to check the adequacy of the developed models. The results of the present work reveal that the feeding speed and duty factor are the most vital factors controlling the metal removal rate. Water pressure has been found to have a sensible effect of MRR especially at a higher feeding speed. Further, the minimum tool wear rate has been obtained at the parametric combination of low feeding speed and low duty factor. In general, it has been found that the increase of water pressure, wire tension and wire speed decreases tool wear. It has also been clarified that the increase of wire tension and wire speed leads to a relatively insignificant change in surface quality.