Hot deformation behavior of Ti-22Al-24Nb alloy was investigated in the temperature range of 900~1110 ℃ and strain rate range of 0.01~10 s-1 employing Gleeble-3500 thermo-mechanical simulator. Characteristics of flow stress curve at elevated temperature and hot deformation activation energy in different phase regions were analyzed, and hot forming parameters of the alloy were optimized by processing maps under instability criterion of Prasad and Murty and corresponding organizational characteristics. The results show that the flow stress of the alloy is sensitive to the hot forming parameters. By the calculation of Arrhenius power function equation, the deformation activation of the alloy is 406.25 kJ/mol in B2 single-phase region that can be a large difference between with (α2+B2) two-phase region(603.56 kJ/mol), which indicates that there may be different deformation mechanisms between different phases regions. According to the comparison of two kinds of processing maps and the microstructure observation, processing map of the alloy based on the Prasad instability criterion is more reasonable. The corresponding main instability zones are 900~990 ℃、0.2~10 s-1 and 1035~1095 ℃、1~10 s-1, and the adiabatic shear bands and the local plastic instability in the microstructure were predicted by the instability zones. However, the dynamic recrystallization and the microstructure of the cellular substructure are easy to appear in the η peak regions, indicating that the better thermodynamic parameter range are 990~1035 ℃、0.01~0.03 s-1, 1040~1090 ℃、0.02~1 s-1 and 1090~1110 ℃、0.01~0.18 s-1.