• One pass repetitive upsetting-extrusion(RUE) apply to process AZ80 Mg bars under different deformation parameters. • A weaker fiber texture is developed via RUE of extruded bars due to the application of interactive stress state. • Deformation parameters affect microstructure evolution, acting on strength, plasticity and anisotropy of extruded bars. • The tensile yield anisotropy of extruded bars is greatly reduced due to texture dispersion and grain refinement. [Display omitted] Repetitive upsetting-extrusion (RUE) is known as a processing method that effectively improves the properties of a billet without changing its initial shape. In this paper, one pass RUE with reduced deformation temperature (re-upsetting at 360 °C and secondary extrusion at 340 °C) and different extrusion speeds (0.5 and 1 mm/s) is implemented to improve the strength and toughness of AZ80 Mg rods, and simultaneous reduction in tensile anisotropy is achieved. Influences of one pass RUE method on the resulting microstructure and texture evolution of the alloy are investigated alongside their correlated impact on its mechanical properties. After RUE processing, the grain structure of AZ80 alloy is characterized by numerous fine dynamic recrystallized (DRXed) grains, combined with large unDRXed grains obtained at high extrusion speed or coarse DRXed grain bands obtained at low extrusion speed. Besides, β-Mg 17 Al 12 particles dynamically precipitated during deformation, acting as strong barrier against grain boundary migration through pinning effect. Through introduction of an interactive stress state, the RUE process promotes dispersion of the fiber texture that typically develops during the extrusion process. The key factor that promotes weakening of the fiber texture is derived from the refinement of basal orientated deformed grains, which form during upsetting deformation, into numerous non-basal orientated DRXed grains during early-stage extrusion. Compared with coarse deformed grains, these fine DRXed grains delay transformation of texture into the typical [10-10]–[11-20] fiber component. Grain refinement is implicated as the most significant factor with respect to simultaneous improvement of strength and toughness in the extruded rods, while tensile yield anisotropy in response to loading along the ED and TD is attributed to unDRXed grains with [10-10] fiber orientation. Compared to the as-cast state, extruded rods demonstrate increases in yield strength, ultimate tension strength, and elongation maximally up to ~2.6, ~2.2, and ~4.9 times, respectively. And when complete DRX structure is nearly achieved, the tensile yield anisotropy of extruded bar is effectively eliminated because the refined grains with relatively dispersed orientation inhibit the nucleation of tension twin and simultaneous enhance the Hall-Petch effect. [ABSTRACT FROM AUTHOR]