Abstract: The service performance of titanium alloy component is affected by its microstructure, and the microstructure of alloy is determined by the hot forming process. Therefore, in order to obtain the influence mechanisms of forming process on the high-temperature deformation and microstructure evolution of titanium alloy, for damage tolerant TC21 titanium alloy, the isothermal thermal compression tests were carried out at the deformation temperatures of 900 and 940 ℃, the strain rates of 0.001,0.01,0.1 and 1 s-1 and the reduction amount of 60%. Then, based on the experimental results and the dynamic recrystallization theory, the high-temperature deformation behaviors of the alloy were obtained, and the evolution laws of dynamic recrystallization were analyzed by constructing a dynamic model. The results show that the thermal deformation behavior of TC21 titanium alloy is influenced by both deformation temperature and strain rate, and its dynamic recrystallization process conforms to the Avrami kinetic equation. At the same strain rate, the dynamic recrystallization rate is faster at higher deformation temperature, while at the same temperature, the dynamic recrystallization rate is smaller at the lower strain rate.