In this study, quasi-in-situ electron backscatter diffraction was employed to investigate the microstructural evolution and deformation behaviour of ZK60 magnesium alloy with an initial 45° extruded state orientation under two high-speed impacts. The experimental results demonstrated that the deformation of the alloy mainly depended on slip and [Formula: see text] tension twinning. With the increase of deformation, the [Formula: see text] tension twins nucleated continuously, and there were stretching twin variants that were 60° away from the original stretching twins. In addition, compared with the conventional orientation (extrusion direction), 45° samples were easier to activate various slips under high-strain rate deformation conditions, especially ⟨c + a⟩ slips.