Improving the mechanical properties of Mg alloys is of great significance for their wide application. A micro-alloyed Mg-1.45Bi-0.79Ca alloy (in wt.%) exhibiting a high tensile yield strength of 394 ± 5 MPa and a moderate elongation of 6.6 ± 0.6% was fabricated by single pass extrusion. The superior high strength is mainly attributed to the synergy effects of ultra-fine dynamic recrystallized grains; numerous Mg₂Ca, Mg₃Bi₂, and Mg₂Bi₂Ca nano-precipitates; residual dislocations; sub-grain boundaries; as well as strong fibre texture in the extrusion direction.