Melt hydrogenation was presented based on thermal hydrogenation processing (THP). Titanium alloy was melted in H2/Ar gaseous mixture. Part of hydrogen was absorbed by the alloy after cooling. Compared with THP, the hydrogenation process was very fast because of the big diffusion coefficient in melt alloy. The relationship between hydrogen content in TC21 alloy and partial pressure of H2 was deduced based on Sievert’s law. It is found that the grain size and microhardness of TC21 alloy are decreased with more hydrogen. With the hydrogen content further increasing, α" phase and twining structure is detected in the alloy.