Abstract: Electron beam selective melting manufacturing technology is an additive manufacturing technology that uses high-speed deflection scanning of electron beams to achieve substrate preheating, powder preheating and powder melting,ultimately achieves near-net shape of complex structural parts. However, large angle deflection can cause the electron beam stroke to increase, and the aberration of the electron beam spot will appear, which affects the heat input of the part and leads to poor forming quality. A 1∶1 three-dimensional model of the electron beam selective melting equipment was established, and the entire beam generation process was simulated using the CST electromagnetic simulation particle studio. Aiming at the problems of poor morphology of electron beam after large angle deflection, the high-speed deflection, dynamic focusing and astigmatism coils for the electron beam were designed to achieve synchronous adjustment of the beam quality of the beam spot. The combination of beam quality simulation and actual processing verification proves that the synchronous adjustment has greatly improved the quality of formed parts.