For common material as-cast Cr5 steel for back-up rollers, based on the single-pass thermal compression test, its thermal deformation behavior and thermal processing map under different test parameters were analyzed and studied, and in the test, the deformation temperature was 850-1220 ℃, the deformation rate was 0.01-1 s-1, and the true strain was 0.7. Then, the true stress-true strain curve of as-cast Cr5 steel was drawn by the test data, and the factors affecting the rheological stress were obtained. Furthermore, the undetermined material coefficients were calculated by fitting the curves, and the rheological stress equation of as-cast Cr5 steel was given. Finally, based on the true stress-true strain curve, the thermal processing map in the strain range of 0.1-0.6 was drawn. The results show that increasing the deformation temperature and decreasing the strain rate can reduce the rheological stress of Cr5 steel, which is conductive to the occurrence of dynamic recrystallization. With the increasing of strain, the instability area and power dissipation factor become larger, and the optimum processing parameters range of Cr5 steel at high temperature is the deformation temperature of 1000-1200 ℃ and the strain rate of 0.03-0.37 s-1.