Abstract: The influence of working chamber pressure (1 333.22-133.32 Pa) with the accelerating voltage of 100 kV and the beam current of 80 MA on the electron beam shape and welding process was investigated to solve the severe problem of electron beam scattering in the low vacuum welding and local vacuum electron beam welding process. The method of electron beam welding with coaxial helium protection was proposed. The effect of vacuum degree on the shape of the electron beam was studied under the condition of no protection and helium protection, respectively. Sound welded joints were obtained by electron beam welding with coaxial helium protection.