The thermal parameter boundary conditions of the unstable deformation microstructure and dynamic recrystallized microstructure of BT25 titanium alloy were determined by the instability maps and power dissipation maps, respectively. The results were used in the Deform-3D finite element (FE) software to effectively combine the processing map technique with FE technique. The FE codes after secondary development were used to simulate and predict the unstable deformation zones and dynamic recrystallization (DRX) behavior of BT25 titanium alloy at the deformation temperature of 950~1100 °C and the strain rate of 0.001~1 s^-1. The reliability of simulation results was verified by metallographic microstructure. Results show that the flow stress is decreased with increasing the deformation temperature or decreasing the strain rate. The unstable deformed microstructure is concentrated in the region of low temperature and high strain rate. Both high temperature and low strain rate are beneficial to DRX behavior. The results of metallographic microstructure are in good agreement with those of simulation, indicating that the method of combining processing map technique and FE technique is reliable and feasible for predicting the unstable deformed microstructure and DRX behavior in the metal forging process.