Abstract: The electron beam surface modification is a new type of surface modification technology which can bombard the surface of metal materials with high-energy electrons to make them melt quickly. By mathematical modeling of electrons in the deflection magnetic field, key parameters such as the number of turns of the deflection coil, the outer diameter of the tube neck, and the length of the magnetic circuit were determined to realize the control of the deflection angle and frequency of the electron beam, and the loop was quantitatively analyzed. The influence of electron beam scanning frequency on the surface temperature field and morphology of 45 steel in the downward beam mode were analyzed. The results show that the ring-shaped downward beam method can realize large-area electron beam surface modification, and the energy density is evenly distributed. The surface temperature under the action of the high-frequency electron beam is higher. The beam spot temperature at the front end of the moving direction is higher and the molten metal is concentrated. The milling scratches on the surface of the sample after beam scanning completely disappear, and the surface roughness drops to 0.487 μm.