Stress-grading systems are essential for the suppression of corona in the end-turn zone of high voltage rotating machines. Unfortunately, design of stress-grading systems in industry is almost entirely based on experimental trial-and error techniques. This paper introduces a novel graphical user interface (GUI) model for the selection and design of stress-grading systems of high voltage rotating machines. The GUI model is based on two major design approaches for stress-grading systems: i: minimization of power-loss and, ii: time-domain analysis of nonlinear stress-grading systems using the describing function method. Comprehensive codes written in both FORTRAN and MATLAB® were developed for the purpose of design and analysis of linear and nonlinear stress-grading systems of high voltage rotating machines. A GUI was developed to enable the design engineer to select analyze and optimize stress-grading systems. This graphical front-end to FORTRAN and MATLAB® codes utilizes built-in functionality of MATLAB® to create graphical interface objects, interface with compiled FORTRAN functions, and generate design and analysis reports based on the data gathered from the source codes.