Vacuum electron beam welding was used to realize the full thickness welding of Ti-6321 (nominal component Ti-6Al-3Nb-2Zr-1Mo)titanium alloy with 94mm large thickness.The full thickness of the welded joint can be well formed with the method of bottom locking at the bottom. The welded joint shows approximately parallel weld morphology, and the depth width ratio is about 16.The results show that the weld center is composed of coarse columnar crystal and internally staggered acicular α and α" phase.The transition from coarse grain to fine grain near the fusion zone. The width of unilateral heat affected zone is about 2 mm. The microhardness of the weld zone and the heat affected zone were both lower than that of base metal.The tensile strength of welded joint was equivalent to that of the base metal, and the fracture occured in the weld metal.Both the weld zone and the heat affected zone have better impact toughness.The strength and toughness of the welded joint are excellent.The mechanical properties in the direction of welded joint have good uniformity.