Isothermal uniaxial tension tests for O phase-based Ti-22Al-25Nb alloys were conducted at 1203–1283 K with temperature interval of 20 K. The strain rates were 2.5×10^-4, 5.0×10^-4, 1×10^-3, 2×10^-3, 4×10^-3, 1×10^-2, and 5×10^-2 s^-1. The microstructures of specimens at different deformation temperatures were characterized. Through the experiment results, the material constants for the constitutive models are determined and the tensile deformation activation energies are 845 165 and 412 779 J/mol at α₂+B2/β+O three-phase region (1203–1243 K) and α₂+B2 two-phase region (1243–1283 K), respectively. Arrhenius-type constitutive models are constructed to characterize the tensile deformation behavior of Ti-22Al-25Nb alloy at different temperatures.