The amount of energy required to harvest Napier grass and the quality of the cut depend on the blade angles. Hence, it is crucial to analyses the impact of different cutting blade angles, including the bevel angle, shear angle, and approach angle, on both the specific cutting energy (SCE) and cutting index (CI) of Napier grass. Therefore, to achieve minimum specific cutting energy (SCE) and cutting index (CI), the optimization of blade angles was carried out. The study employed a pendulum-type impact testing apparatus to investigate the impact of operational parameters of the cutting blade on the SCE and CI for Napier grass. In addition, the current study utilized the response surface method for analysis and optimization purposes. The optimum operational parameters were found to be bevel angle of 15°, shear angle of 20.74°, and approach angle of 30°, which predict the minimum SCE of 19.84 kJ m−2 and CI of 1.89. The performance of the pendulum testing machine was validated by setting optimum conditions. It was found that the SCE was 20.20 kJ m−2 along with CI of 2. This result shows that the validated results are closer to predicted result. In future research, it is crucial to evaluate the cutting element’s performance in the Napier grass harvester under the aforementioned conditions. Additionally, a thorough investigation into the influence of the cutter’s peripheral velocity and the prime mover’s forward speed on the SCE requirements of grass is essential.