Alloying design and grain refinement strategies have emerged as promising synergistic approaches to overcoming the persistent strength–ductility trade-off that occurs during Mg alloy processing. However, the regulatory effect of plastic deformation on microstructural evolution requires further systematic investigation to synergistically optimize mechanical performance. In this study, multi-pass and single-pass hot compression tests were performed on Mg–Gd–Y–Nd alloys that had been rapidly solidified, and the key parameters for alloy design in big data research—dynamic recrystallization (DRX), geometrically necessary dislocation (GND) density, and texture—were analyzed using EBSD and Wulff net. The results show that a split texture in the transverse direction (TD) (in the Wulff net coordinate system, the peak distribution is in the ranges of 20° ≤ φ ≤ 40° and 50° ≤ θ ≤ 70°, where θ represents the radius, φ denotes the latitude) was formed during the multi-pass hot compression. The primary factors that affect the formation of TD split texture are the reduction in the number of grains having a 2° correlated misorientation angle, the increase in the fraction of soft-oriented grains, and the reorientation of grains into positions that are favorable for activating the prismatic <a> slip. In contrast, the results showed that a split texture in the extruding direction (ED) (in the Wulff net coordinate system, the peak distribution is in the ranges of 60° ≤ φ ≤ 70° and θ ≈ 80°) was formed during single-pass hot compression. The primary factor that affected the formation of the ED split texture was the need for a significant number of grains to reorient to positions that were favorable for activating the pyramidal <c + a> slip to coordinate the deformation of the c-axis during single-pass hot compression. The splitting texture of magnesium alloys enhances both strength and plasticity. The TD split texture involves orienting the c-axis of the grains toward the TD. When a load is applied in the TD direction, the deformation is primarily coordinated by the activation of the pyramidal <c + a> slip (with a high critical resolved shear stress (CRSS)), which is beneficial for enhancing strength. When a load is applied in the non-TD directions (i.e., the ED and normal direction (ND)), the deformation is coordinated by the prismatic <a> slip and basal <a> slip (with a lower CRSS than the pyramidal <c + a> slip), which is beneficial for enhancing plasticity. With an ED split texture, the c-axis of the grains are oriented toward the ED. When a load is applied in the ED direction, the deformation is primarily coordinated by the activation of the pyramidal <c + a> slip, which is beneficial for enhancing strength. When a load is applied in the non-ED directions (i.e., the TD and ND directions), the deformation is coordinated by the prismatic <a> slip and basal <a> slip, which is beneficial for enhancing plasticity. The recrystallized grain fraction during multi-pass hot compression was 16% and was accompanied by a higher GND density (4.59 × 10¹³ m⁻²) than during single-pass hot compression (4.20 × 10¹³ m⁻²), as well as a significant weakening of the mixed crystal structure. This outcome was primarily attributed to the alternating occurrences of continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) during multi-pass hot compression. In contrast, during single-pass hot compression, the recrystallized grain fraction was 14% and larger micron-sized substructures were retained (which led to the formation of the mixed crystal structure). This outcome was primarily attributed to the dominance of DDRX during single-pass hot compression.