Abstract The effects of hydrogen on the hydrogen embrittlement of Ti-2Al-2.5Zr alloy was investigated by tensile test, slow strain rate test (SSRT), and the amount of absorbed hydrogen of Ti-2Al-2.5Zr alloy was studied by immersion test in alkaline steam water at a pressure of 8.5MPa. The results indicated that the hydrides(TiH2) in Ti-2Al-2.5Zr alloy formed as platelets and were identified as face-centered cubic δ-hydride. At room temperature, hydrogen and formed hydrides induced increase of the intensity and caused loss in the ductility. In alkaline steam water at a pressure of 8.5MPa, the hydrogen embrittlement susceptibility index (IHE) of Ti-2Al-2.5Zr alloy increased with increasing hydrogen content, and the IHE value of the alloy with 350ppm H was less than 0.1. Moreover the amount of absorbed hydrogen of Ti-2Al-2.5Zr alloy increased with increasing of immersion time, and absorbed hydrogen was still less than 50ppmH even when immersion time reached 13000h.