Abstract: The 2 mm thick Ni-Ni3Si hypereutectic alloy plate was welded by electron beam welding. The influences of different parameters on the weld appearance were studied. And the contributions of electron beam and weld speed were clarified. The results showed that the weld widths of back side and top side and the ratio of the two side increase with the increase of beam current and the decrease of welding speed. The weld appearance turns to be a goblet-like shape at high welding speed and low beam current. The welding speed is significant for the top side weld width while the beam current is more significant for the back side weld width and the ratio of weld back width and weld top width.