Electron beam fuse additive manufacturing technology is suitable for efficient integrated forming of large and medium-sized metal components. Aiming at the many shortcomings of electron guns currently used for additive manufacturing,an annular beam spot cold cathode electron gun was designed,a three-dimensional model was established,and the structural dimensions of the key components of the beam source were simulated. When the radius of the cathode arc is 100 mm and the anode inclination angle is 40°,the beam quality is the best. According to the simulation results,the actual electron gun was manufactured. After testing,the designed electron gun can withstand voltage up to -22 kV and beam current up to 1250 mA. The 2 mm diameter TC4 welding wire was selected for fuse test with accelerating voltage of -20 kV,beam current of 210 mA,table moving speed of 310 mm/s and wire feed speed of 30 mm/s, and a good surface forming quality is obtained.