The purpose of this project is to study the encouragement of three machining parameters on wire electrical discharge machining that consist of peak current (IP), pulse OFF time (OFF) and wire tension (WT) to three machining responses which are cutting rate (CR), material removal rate (MRR) and surface roughness (SR) on high carbon steel (S50C). Brass wire with diameter 0.25 mm was used as the cutting tool for machining a high carbon steel (S50C) using Mitsubishi FX Wire Electrical Discharge Machine (WEDM). The machining parameters such as pulse off time, wire tension and peak current were determined by referring from the guideline in the manual book for Mitsubishi FX Wire Electrical Discharge Machine (WEDM). The calculation of material removal rate and cutting rate were obtained using mathematical equation. The surface roughness was measured using optical measurement “Alicona Infinite Focus” machine. The relationship between material removal rate and surface roughness shows that the optimum machine parameter using brass wire as the electrode is C1. From the spark analysis using brass wire as the machine’s electrode, the deeper the spark occurred, the higher value of the surface roughness.