The deformation flow behaviors of Ti-45Al-5.4V-3.6Nb-0.3Y alloy at different temperatures and strain rates were studied by isothermal compressing simulation test. The apparent activation energy of deformation was calculated to be 402.096 kJ/mol and constitutive equation was established to describe the flow behavior. Microstructure and flow softening observations exhibited that Ti-45Al-5.4V-3.6Nb-0.3Y alloy had bad hot workability at low temperature (lower than 1 100 ℃) and high strain rate (higher than 0.5 s-1) characterized by localization deformation and instability. With deformation temperature higher than 1 150 ℃ and strain rate lower than 0.01 s-1, the alloy owned good hot deformability, and plenty of dynamic recrystallized grains could be observed in the deformed microstructures.