Low-temperature slow rate extrusion (LTSRE) and electrical pulse treatment (EPT) were carried out to obtain a bimodal microstructure in AZ91 Mg alloy, which consisted of coarse un-recrystallized grains of about 20-60μm and fine recrystallized grains of around 200nm. The bimodal grains can be contributed to the inhomogeneous deformation under LTSRE and the acceleration effect of the static recrystallization of the deformed AZ91 magnesium alloy under EPT. In addition, the growth of the recrystallized grains was effectively restrained due to the notably lower recrystallization temperature and shorter processing time compared with the conventional static recrystallization by heat treatment. Meanwhile, abundant Mg₁₇Al₁₂ phase with an average size of 200nm and regular shapes precipitated during EPT. Consequently, the exceptional yield strength of 463MPa and ultimate tensile strength of 527MPa were acquired in the bimodal AZ91 alloy, which can be primarily attributed to the bimodal microstructure as well as the combined effect of fine grain strengthening, precipitation strengthening and work hardening.