Abstract: The strength-plasticity tradeoff of magnesium (Mg) alloys is a crucial factor restricting their widespread application as structural materials. In this work, simultaneous enhancement of strength and plasticity in an extruded Mg-4Zn-0.5Sn (wt. %) alloy is achieved via simple double pre-compression (DPC) along the transverse direction. After applying DPC-6 %, the yield strength increased by 81 % to 206 MPa, and elongation increased by 17 % to 28 %. The enhanced strength is primarily attributed to grain refinement strengthening (matrix), twin strengthening, dislocation strengthening and back stress strengthening. The glide of 〈c〉 component dislocations and 〈c + a〉 dislocations introduced by DPC during tensile coordinates the c-axis strain, thereby promoting uniform plastic deformation. Forward stresses developed in the high-strain region of the multi-scale strain gradient zone facilitate plastic deformation in the adjacent hard-to-deform zone. This study provides a simple strategy for manufacturing high-performance Mg alloys.