To investigate the dynamic mechanical behavior of AZ31 Mg alloy, dynamic compression was carried out using a split Hopkinson pressure bar （5HPB） apparatus at strain rates up to 2.0 × 10^3 s^-1, and dynamic hardness was tested employ- ing a dynamic hardness device at room temperature. Microstructural characteristic was analysed by optical microscopy. The dynamic compression results demonstrate that AZ31 Mg alloy exhibits obvious yield phenomena and strain hardening behav- ior at high strain rates. The basically same curvature of stress-strain curves shows a similar strain hardening rate. The dy- namic yield strength changes little, and the peak stress increases with the strain rates. The dynamic hardness test results indi- cate that the dynamic mechanical properties of AZ31 alloy sheet are anisotropic. The dynamic hardness increases slowly with average strain for the 0° and 45° oriented samples. For the 90° oriented sample, dynamic hardness with strain increases rapidly first and then decreases when the strain is more than 0.14. An examination by optical microscopy after high strain rate deformation reveals the occurrence of twinning, and the twin area percentage escalates with the strain rate increasing.
