The hot tensile behavior of Ti-22Al-24.5Nb-0.5Mo (at.%) alloy was investigated by the hot tensile tests at the temperature 910-1040°C and the strain rate 0.0001s-1-0.1s-1. The Arrhenius equations were calculated at the three different phase fields and the microstructure evolution mechanisms were studied by microstructure observation. The results show that the activated energies were 759.43kJ/mol, 516.71kJ/mol and 438.59kJ/mol at B2/β+O, α2+B2/β+O and α2+B2/β phase fields, respectively. The microstructure evolution were dominated by dynamic recrystallization of O-phase and dynamic recovery of B2/β phase grains, and the softening mechanism was the globularization of O lamellar grains at B2/β+O phase field, while the softening mechanism was dynamic recrystallization and shear bands of the B2/β-phase grains α2+ B2/β+O.