Abstract: Electric Power Steering (EPS) is a full electric system, which reduces the amount of steering effort by directly applying the output from an electric motor to the steering system. This study aimed at developing EPS boost curve embody into the assist characteristics, improving steer portability and stability. A model for the EPS system had been established, including full vehicle mechanical system, EPS mechanical system and EPS electric control system. Based on this model, a straight line boost curve was designed and evaluated in this environment to improve the performance of EPS system. Based on the designed curve, EPS control model was established by integrating ADAMS and MATLAB. The co-simulation system was applied to evaluate the performance of EPS system. Simulations were conducted under double lane change and returning condition. Even with preliminary study, results showed that the designed curve under PID control can provide higher performance in control stability, which indicated the positive effect of designed EPS boosting curve on higher vehicle performance.