Abstract: Electron beam welding of TC4/Ta-W alloys is studied; the beam is offset to the Ta-W alloy side as welding. The appearance of electron beam welded joints is good, the content of Ta and W elements is high in certain beam offset, the weld microstructure is solid solution based on β-Ti, there are no brittle compounds to generate but there is the existence of rich Ta zone and poor tantalum zone. The distribution of elements in the weld is uneven, the content of titanium in weld is relatively high, about 60%, when the optimal beam offset is 0.6 mm, but the basemetal of tantalum and tungsten is relatively small to be melted, about 40%. The optimal tensile strength of the joints with beam offset 0.4 mm is 714 MPa, which almost is equal with basemetal. The fracture occurs at the weld. The hardness in heat-affected zone of Ta-W alloy side is lower than that in the basemetal, and the maximum hardness appears at the fusion line of Ti side.