The mechanical properties of the Mg97Zn1Y2 extruded alloy containing the long-period stacking ordered phase,the so-called LPSO-phase,with a volume fraction of 24%-25%,were examined by compression tests and cyclic tension-compression deformation tests.The plastic behavior of the extruded alloys with compositions of Mg99.2Zn0.2Y0.6 and Mg89Zn4Y7(molar fraction,%) ,which were almost the same compositions of Mg matrix phase and LPSO phase in Mg97Zn1Y2 Mg/LPSO two-phase alloy,respectively,were also prepared.By comparing their mechanical properties,the strengthening mechanisms operating in the Mg97Zn1Y2 extruded alloy were discussed.Existence of the LPSO-phase strongly enhanced the refinement of Mg matrix grain size during extrusion,which led to a large increment of the strength of alloy.In addition,the LPSO-phases,which were aligned along the extrusion direction in Mg97Zn1Y2 extruded alloy,acted as hardening phases,just like reinforced fibers. The mechanical properties of the Mg97Zn1Y2 extruded alloy containing the long-period stacking ordered phase, the so-called LPSO-phase, with a volume fraction of 24% -25%, were examined by compression tests and cyclic tension-compression deformation tests. plastic behavior of the extruded alloys with compositions of Mg99.2Zn0.2Y0.6 and Mg89Zn4Y7 (molar fraction,%), which were almost the same compositions of Mg matrix phase and LPSO phase in Mg97Zn1Y2 Mg / LPSO two-phase alloy, respectively, was also prepared.By comparing their mechanical properties, the strengthening mechanisms operating in the Mg97Zn1Y2 extruded alloy were discussed. Existence of the LPSO-phase strongly enhanced the refinement of Mg matrix grain size during extrusion, which led to a large increment of the strength of In addition, the LPSO-phases, which were aligned along the extrusion direction in Mg97Zn1Y2 extruded alloy, acted as hardening phases, just like reinforced fibers.