The dynamic compressive constitutive relation of metallic Neodvmium(Nd) over a wide range of strain rates at different temperatures was determined in the first loading duration of split Hopkinson pressure bar(SHPB) tests. The determined constitutive relation in a certain range of strains for metallic Nd was employed and adjusted in numerically simulating large deformations of Nd specimens generated by the multi-compressive loadings during SHPB tests, and recorded by a high-speed camera. The shearing instabihtv strain in dynamic compressive deformations of metallic Nd was estimated with the adjusted constitutive relation according to the criterion given by Batra et al，and was compared with the average strain of recovered specimens.