The thermal deformation behavior and heat processability of Ti80 alloy with bimodal microstructure was discussed in temperature of 860 ~ 1020 ℃, strain rate range of 0.001 ~ 10 s_-1 and maximal deformation of 50% by hot simulator, optical microscope and MATLAB software. Results showed that Ti80 alloy is negative temperature and positive strain rate sensitive material. Main softening mechanism changes from dynamic recrystallization to dynamic recovery when temperature increases. In addition, the train compensation constitutive equation and processing map were constructed by MATLAB programming. Correlation coefficient R between the predicted value and the experimental value of constitutive equation is 0.994, and average relative error AARE is 7.443%. The optimum processing parameters interval of Ti80 alloy is [980 ~ 1015 ℃]-[0.013 ~ 0.100 s_-1], which peak of power dissipation h is 64%.