This paper focuses on the AZ31 magnesium alloy, utilizing single-pass hot rolling to fabricate an alloy with the bimodal grain structure, and examines how this structure enhances the alloy’s strength and plasticity. The experimental results show that the formation of the bimodal grain structure is more pronounced at rolling temperatures ranging from 350 ℃ to 450 ℃, especially under conditions of large reduction (≥40%). The optimized proportion and distribution of the bimodal grain structure play a pivotal role in simultaneously enhancing the alloy’s strength and ductility, significantly impacting the mechanical properties. The rolled sheet with the bimodal grain structure achieved an ultimate tensile strength of 258.3MPa and an elongation of 17.1% under a rolling reduction of 40%, with a rolling rate of 75 m/min and a rolling temperature of 400 ℃. Adjusting rolling parameters, including temperature, reduction ratio, and rolling rate, is crucial for optimizing the bimodal grain structure, thereby achieving a balance between improved plasticity and maintained high strength.