Abstract: A series of numerical simulations of SHPB test using 921A steel pure shear hat-shaped specimens are conducted with ANSYS/LS-DYNA and validated by the SHPB tests in the present paper. Integrated with the theory of stress wave in a SHPB system,the wave propagation in the bars and the dynamic deformations of the specimen under different loading rate (or stress pulse ) are analyzed,and typical wave shapes are identified for different loading rates. Numerical test of SHPB under ultrahigh strain rate are specially conducted,which is unable to be done realistically. The different deformation and failure of the hat-shaped specimens under different loading rate are distinguished,and the applicability of strain waves in the bars under ultrahigh loading rate is also discussed.