Abstract: Dynamic compression behavior of extruded AZ31 magnesium alloy at high temperature were studied using the system of separated hopkinson pressure bar, and the microstructure evolution before and after dynamic compression was analyzed and the effects of temperature and loading direction on dynamic compression behavior and microstructure were discussed. The results show that, for loading direction parallel to extrusion direction specimens, true stress-true strain curve presented descend trends with the increase of temperature;however, as for loading direction perpendicular to extrusion direction samples above 200 ℃, temperature had no significant influence on true stress-true strain curve. Besides, the mechanism of dynamic recrystalization during the dynamic compression process could be attributed to twin nucleation and dislocation nucleation. Deformation mechanism gradually transferred from twinning to slip with the increase of temperature, and this phenomenon was more obvious for loading direction perpendicular to extrusion direction samples. Primitive mischcrystal structure could be refined remarkably by compression deformation at temperature of 300 ℃.