Using the experimental data obtained by isothermal and constant strain rate compression of the SP700 titanium alloy under the Gleeble-3800 thermal simulation test machine, the instability map based on the Prasad instability criterion is constructed. The boundary conditions for the thermal compression instability deformation of SP700 titanium alloy when the deformation temperature is 700 ~ 950 ℃ and the strain rate is 0.001 ~ 1 s_^-1 are obtained. Based on this, combined with Deform-3D finite element software to analyze the SP700 titanium alloy in the process of hot compression, the distribution and change of the unstable deformation area are studied by finite element numerical simulation.The results show that the microstructure of the SP700 titanium alloy obtained by the hot compression experiment is in good agreement with the finite element numerical simulation results. The Deform-3D finite element software can effectively simulate and predict the distribution and change of the unstable deformation area of the SP700 titanium alloy during the hot compression process.