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By using MTS(Mechanical Threshold Stress)model and the experimental technique of the split Hopkinson bar with the synchronization assemblage,the dynamic constitutive equation of the unidirectional-solidified horizontal-continuous-casting polycrystal copper was investigated.In the narrow heated furnace designed and manufactured by NPU,the dynamic impact experiments at tempera-ture from 287 K to 1100 K were accomplished.The optimized parameters of the dynamic constitutive equation applying to the unidirectional-solidified horizontal-continuous-casting polycrystal copper were obtained and the theoretical stress-strain curves had a good agreement with experimental curves at temperature from 685 K to 1085 K.The concept of restoration threshold energy was proposed and the parameters of MTS model were also discussed in detail.The results show that only seven parameters in parameters of MTS model are independent and MTS model is not very good to describe the discreteness of mechanical properties,restoration,recrystallization and associated strain softening at temperature from 287 K to 685 K.