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The formation and evolution of adiabatic shear bands in U-5.7Nb alloy deformed at a strain rate of 8 000 s-1 were investigated in this paper．Dynamic deformation at different strain values of U-5.7Nb alloy were obtained by means of the strain stopping rings and the controlled strain rate．The experimental results show that two types adiabatic shear bands in U-5.7Nb alloy under dynamic deformation were distinguished as the strain increasing．The critical strain value for the deformed band formation was adjacent to the 0.33,and the corresponding critical strain value for the transformed band formation was close to 0.39．Microstructural observation shows that the deformed bands were composed of the severe deformed and elongated grains,and the transformed bands mainly composed of the ultrafine and equiaxed grains were confirmed. Based on characterization of adiabatic shear bands at different strains, the plastic deformation and fracture process of U-5.7Nb alloy subjected to dynamic loading were speculated.