<p>Pre-deformation is a low-cost and effective method to improve the comprehensive mechanical properties of magnesium alloys. In order to clarify the effect of pre-deformation on the adiabatic shear behavior of magnesium alloys, a commercially extruded AZ31 magnesium alloy sheet is pre-deformed by quasi-static compression along transverse direction (TD), and then impacted by high strain rates deformation with separated Hopkinson pressure bar (SHPB). Microstructure before and after deformation are characterized by optical microscopy (OM), backscattered electron diffraction (EBSD) and transmission electron microscopy (TEM). The results show that the adiabatic shear sensitivity of AZ31 alloy is increased with the increasing of the pre-deformation strain, which is reflected in the advancement of stress collapse and the transition process from the deformation shear band to the transformation shear band. According to the degree of recrystallization, the adiabatic shear band can be divided into two areas: the central area (CA) and the transition area (TA). The CA is mainly composed of fine recrystallized grains, while part of grains own energy is attributed to recrystallized grains are still continuously loaded and deformed again. Pre-deformation strengthened the grains refinement effect of CA; however, increasing pre-deformation is ineffective for further grain refinement. The TA is composed of deformed grains, twins, and part of recrystallized grains. The closer to CA, the more recrystallized grains and greater stress concentration exist. The enhanced adiabatic shear sensitivity of the material with pre-deformation is mainly related to the part of the energy provided by the pre-deformation for the formation of subsequent adiabatic shear bands.</p>