The effect of hydrogenation on microstructure and phase transformation of TB8 alloy was investigated by OM, SEM and XRD, and the variation of hardness after hydrogenation was studied. The result reveals that the amount of β phase increases gradually as the hydrogen content increases and hydrogenation reduces the critical cooling rate of ω phase. The hardness of TB8 alloy first increases and then decreases with increasing of hydrogen, which is attributed to the interaction of hardening phase ω, hydride δ, softening phase β and solid solution strengthening of H.