The electropulse-assisted forming process has been widely used in various plastic deformation applications owing to its advantages in improving formability and refining microstructure. However, the influence of electropulse on the dynamic extrusion deformation process remains unclear. In this study, the effects of electropulse on dynamic precipitation and microstructure evolution of AZ91 magnesium alloy during extrusion were investigated using electropulse-assisted extrusion (EPAE) technology. The results demonstrate that under critical deformation conditions for complete dynamic recrystallization, the EPAE process reduces the volume fraction of the β-Mg₁₇Al₁₂ phase, promotes its spheroidization, and enhances both the average grain size and the maximum basal texture intensity. These effects become more pronounced with increasing peak current density. Specifically, with a peak current density of 6.4 × 10⁷ A/m² during the EPAE process, the volume fraction of the β-Mg₁₇Al₁₂ phase decreased from 76.9% to 16.5%, the average grain size increased from 1.07 μm to 3.54 μm, and the maximum basal texture intensity increased from 3.39 to 5.92, compared to conventional hot extrusion. The bimodal structure observed in the EPAE-processed AZ91 alloy was attributed to the pinning effect caused by the inhomogeneous distribution of the β-Mg₁₇Al₁₂ phase. Experimental and theoretical analyses indicated that the increase of Gibbs free energy variation and atomic diffusion flux during extrusion of AZ91 alloy caused by the combined thermal and athermal effects of the pulsed current was the main reason for the experimental phenomena, which promoting the solution of β-Mg₁₇Al₁₂ phase and uniform distribution of Al solute atoms nearby while also increasing the grain boundary migration rate. Moreover, the electropulse strengthened the basal texture in β-Mg₁₇Al₁₂ particle-depleted regions by accelerating basal <a> slip.