Abstract: The diffusion bonding of hydrogenated Ti6Al4V alloy containing 0.15 wt.% hydrogen was carried out, and the phase component of before and after welding, interface structure and the diffusion holes were investigated by means of scanning electron microscope, electron probe microanaly sis and X-ray diffraction.The results showed the phase component of before welding was black strip αplus lamellar (α+βH), and the after was equiaxed αplus the coarse lamellar (α+β)plus hexagonal close packed α'in the β phase.The diffusion of Al and V in αand βH took place during bonding.With the diffusion bonding parameters increasing, the diffusion holes gradually decreased.When bonded at 850℃ for 60 min under a pressure of 12 MPa, the diffusion holes disappeared and the shear strength of the joint was up to 543 MPa.