The paper prepared the cast Ti-6Al-2.5V-1.5Fe-0.15O titanium alloys by the consumable vacuum arc furnace. Thermal simulation experiments are carried out by Gleebee 1500D, and different deformation temperatures (875℃-1100℃),train rates(0.001-1 s_-1)and the same deformation degree(60%) were chose. Then phase equations of two phase and single based on Arrhenius model were built, considering the influence of strain. The processing map was built by DMM and Prasad instability criterion. The results show that the alloy is belonging to negative temperature and normal strain sensitivity material. The average thermal activation energy of two phase is 398.824KJ/mol,which is bigger than the pure titanium. The softening is related to the dynamic recrystallization softening mechanism. The average thermal activation energy of single phase is 210.93KJ/mol,slightly more than the pure titanium,The softening is related to the dynamic recovery. The two flow instability zones appear on the processing map,The adiabatic shearing easily happens at medium temperate from 950℃-1070℃ and the high strain rates from 0.31s_-1 to 1s_-1,The suitable zone for processing is in the strain rates from 0.001s_-1to 0.1_-1 and temperate from 875℃ to 925 ℃.