© 2020 This study analyzed the effect of extrusion parameters on the microstructural evolution and tensile properties of a Mg-8.0Gd-4.0Y-1.0Mn-0.4Sc (wt.%) alloy. The variation in the dynamic recrystallization (DRX) and dynamic precipitation behavior of the alloy under different extrusion parameters were investigated in detail, and the DRX behavior during hot extrusion and strengthening mechanism were revealed. The primary DRX mechanisms are discontinuous dynamic recrystallization (DDRX), continuous dynamic recrystallization (CDRX). The as-extruded alloy with larger extrusion ratio exhibits smaller dynamic recrystallized (DRXed) grains and a high number of fine precipitated particles. With increasing the extrusion temperature, both the average size and volume fraction of DRXed grain increase, but the fine particle fraction decreases. The alloy extruded at 400 °C and ratio of 20:1 shows the superior strength with tensile yield strength of 352 MPa and ultimate tensile strength of 425 MPa, and the alloy extruded at 450 °C and ratio of 10:1 shows higher elongation to failure of 12%. The enhanced strength is mainly attributed to the combined action of strong basal texture, refined DRXed grains and dense distribution of fine particles, on the other hand, the higher fraction of DRXed grains and lower amount of precipitate particles are beneficial to increase the ductility of the alloy.