For any type of machining process, surface integrity and dimensional accuracy is a critical examination for machined material. Electro-discharge machining (EDM) process is the most effective method for surface integrity and dimensional accuracy evaluation of the machined surface. The present research work focused to investigate the influencing of machining parameters (pulse current, pulse on time and duty cycle) on machining of P91 tool steel. During the machining process, quantitively measurement of surface roughness (SR) and surface crack density (SCD) has been considered as surface integrity. Dimensional accuracy is characterized by over cut (OC) in this process of machining. In this study EDM parameters arranged using RSM-based design of experiment, on SCD, SR, and OC and study their individual impact on these response parameters. Pulse current is the most significant factor as compared to other parameters for the machining in EDM. The current work also recommends an optimum setting of system parameters for obtained good dimensional accuracy and surface integrity after P91 tool steel machining with EDM.