The hydrogenated commercially pure titanium and Ti-6AL-4V alloy with 0.11wt%H were diffusion-bonded in the temperature range from 800 to 860 °C. The interface and elements diffusion were observed by OM, SEM and EPMA. The results show that hydrogen significantly improves the rate of diffusion bonding (bonding rate is up to 98% under the condition of 0.11 wt%H at 840 °C). An equiaxed microstructure is maintained due to the addition of 0.11 wt%H after bonding while the higher amount of hydrogen (0.32 wt%~0.48 wt%H) results in a coarse widmanstatten structure. The improved performance of the diffusion bonding induced by hydrogen is mainly attributed to the weak-bond effect and the increase of diffusion coefficient of the elements. The addition of 0.11 wt%H brings one order increase of magnitude to the diffusion coefficient of Al and V element, as well as 40 °C lower diffusion bonding temperature compared with non-hydrogen Ti-6Al-4V alloy.