In order to study the effect of different deformation parameters of thermal processing on the microstructure of TC21 titanium alloy during plastic forming, this paper uses the Gleeble-3500 thermal simulation testing machine to conduct isothermal constant strain rate thermal compression experiments, and studies the TC21 titanium alloy under different deformation conditions. The thermal deformation behavior of TC21 titanium alloy; and based on the microstructure evolution of TC21 titanium alloy during thermal compression, through the derivation of dislocation density model, recrystallization nucleation and grain growth model of TC21 titanium alloy, a cellular automatic Based on the cellular automata model, the dynamic recrystallization behavior of TC21 titanium alloy during deformation in the β single-phase region was simulated and verified. The results show that the flow stress of the alloy increases with the decrease of temperature and the increase of strain rate; according to the analysis of cellular automata simulation results, the dynamic recrystallization volume fraction and deformation temperature of the alloy in the β single-phase region proportional to the strain rate and inversely proportional to the strain rate.