Abstract: In order to research the influence of hydrogen treatment on weld joints of TA15 titanium alloy, the transformations of microstructures and phase compositions in the fusion area of the weld joints at different processes of hydrogen treatment were analyzed using OP, XRD and TEM, and tensile properties of the weld joints at the room temperature were tested.The results showed that δ-hydride was formed, which has a face-centered cubic structure after hydrogenising at 800℃ for 30 min.A lot of metastable phase β (H) and rhombic martensite phase α″were generated in the process of hydrogenizition at 800℃ for 30 min.They decomposed to αand δ phase with eutectoid treatment.After annealing in vacuum, the effect of big grains refinement in the fusion area was very obvious.After annealing in vacuum, the tensile strength decreased and plasticity increased a little.