In order to study the hot deformation behavior and characteristics of TiAl alloy,the hot compressive experiments were conducted in the temperature range from 1 050 ℃ to 1 200 ℃ and at strain rate range from 0. 001 s-1 to 1 s-1 on Gleeble-1500 hot simulator. The flow stress data was acquired by experiments,and the constitutive relationship was established for TiAl alloy. The results show that the flow behavior of TiAl alloy is sensitive to deformation temperature and strain rate. TiAl alloy flow stress demonstrates significant work hardening and softening characteristics in hot compression. The main mechanism of softening occured dynamic recrystallization on the grain boundary first and then extended into the grain by the EBSD observation. Deformation activation energy is 360 kJ/mol by calculation. The flow stress model is obtained by least square method. The flow stress curve based on this model agrees well with the experimental data,the deviation between them is less than ± 5%,and can predict the flow stress precisely.