The effect of hydrogen on the microstructure and high temperature deformation of a Ti3Al based alloy (Ti 24Al 14Nb 3V 0.5Mo(at%) has been studied. The results show that the hydrides as a result of form hydrogenation decompose at high temperatures, introducing some dislocations. The volumn fraction of the O phase decreases due to the addition of hydrogen. Under high temperature deformation, the hydrogen facilitates the dynamic recrystallization of the O phase and dislocation movement in the B2 phase. The activation energy is also reduced. The mechanisms of hydrogen reduced flow stress and increased m value at high temperature deformation are also analyzed in detail.