The Mg–xGa (x = 1, 2, 3 and 5 in mass%) alloys are subjected to high strain rate rolling (HSRR) at 275 °C with the rollingstrain rate of 9.1 s−1 to develop high performance Mg alloy sheets with high plasticity. Effects of Ga content on microstructureand mechanical properties of the Mg–Ga alloys are investigated by SEM, XRD, tensile testing and etc. The Ga additioncan reduce the critical strain of DRX in Mg alloys, which is associated with the reduced stacking fault energy, the increasedtwinning density during deformation and the more DRX nucleation sites during HSRR. With the Ga content increasing from2 to 3%, the reduced DRX degree is attributable to the hindrance of dynamic precipitates. With the Ga content increasingfrom 3 to 5%, the slightly increased DRX degree can be ascribed to the relatively coarse precipitates. The Mg–2 Ga alloysheet, featured with complete DRX, exhibits an ultra-high plasticity (with the elongation to rupture of 36.6%) and a relativelylow anisotropy of yield strength and plasticity. The Mg–5 Ga alloy sheet has the best comprehensive mechanical properties,with the ultimate tensile strength of 292 MPa, yield strength of 230 MPa and elongation to rupture of 30.3%, which can beascribed to the combination of grain refinement strengthening and precipitation strengthening.