Abstract: In electron beam additive manufacturing, the structure and dimensions of electron gun focusing components directly influence beam current density and radius at the focal point, which affects beam quality. This study employs CST simulation software to conduct an in-depth analysis of focusing components, simulating the specific impacts of structural parameters on beam current density and beam radius. Simulation results demonstrate that under constant parameters, as the winding turns of the focusing coil increase from 800 to 1600, the beam radius first decreases then increases, reaching a minimum of 0.816 mm at 1200 turns. When the yoke gap expands from 60 mm to 80 mm, the beam spot radius gradually decreases from 0.834 mm to 0.799 mm. Similarly, increasing the coil inner diameter from 90 mm to 120 mm reduces the beam radius from 0.866 mm to 0.792 mm. Experimental and analytical results indicate that the optimal configuration for achieving peak beam quality comprises: 80 mm yoke gap, 120 mm coil inner diameter, and 1200 turns of coil winding.