The linear friction welding (LFW) performance of hydrogenated Ti-6Al-4V alloy was investigated. The effects of hydrogen on macro-features and axial shortening as well as microstructure of Ti-6Al-4V alloy joints welded by LFW were analyzed. The mechanical properties of joints after dehydrogenation were also examined by tensile test at room temperature. The results indicated that the hydrogenated Ti-6Al-4V specimens containing 0.3~0.4 wt% hydrogen had a better microstructure and plastic deformation ability, which resulted in the optimum welding performance improvement of LFW. The critical power input of LFW could be lowered by addition of hydrogen to Ti-6Al-4V alloy. The results of tensile test showed that joints which experienced thermohydrogen processing possessed the same tensile strength and plasticity as original joints.