Evident　tension-compression　yield　asymmetry　limited　the　potential　use　of　the　extruded　Mg-4.58Zn-2.6Gd-0.18Zr　alloy　as　a　structural　material.　Pre-torsion　deformation　(free-end　torsion)　was　conducted　on　the　extruded　alloy　and　its　effects　on　microstructure　and　tensile-compressive　mechanical　properties　were　investigated　in　this　study.　It　was　found　that　the　as-extruded　alloy　exhibited　homogenous　microstructure　and　＜100＞　-　＜110　＞　double-peak　fiber　texture.　Gradient　structures　along　the　radial　direction　were　formed　after　pre-torsion,　which　contained　gradient　distribution　of　dislocations,　grain　size,　{102}　extension　twin　lamellas　and　texture　components.　＜100＞　-　＜110　＞　double-peak　fiber　texture　was　gradually　weakened　with　the　torsional　angle　increasing　from　90　degrees　to　135　degrees　and　180　degrees,　and　it　was　related　with　the　re-orientation　of　extension　twinning　and　dislocation　movement.　Moreover,　extension　twinning　was　more　easily　to　be　activated　in　grains　with　＜110＞　fiber　texture　component,　and　this　phenomenon　was　revealed　by　calculating　the　global　Schmid　factor　of　extension　twinning　under　pure　shear　stress　state.　Tensile　and　compressive　yield　strength　increased　monotonically　with　the　increasing　torsional　angle.　Meanwhile,　ductility　almost　remained　unchanged.　Tension-compression　yield　asymmetry　was　gradually　reduced,　and　it　was　eliminated　after　180.　pre-torsion,　which　was　attributed　to　the　texture　weakening.　The　studying　provided　a　promising　and　cost-effective　method　to　enhance　yield　strength　and　reduce　tension-compression　yield　asymmetry　while　also　keep　ductility　for　extruded　Mg　alloys.