Mg_(97)Zn_1Y_2 alloy has been studied as an elevated temperature creep resistant Mg-based alloy for nearly ten years.While, the strength of the cast Mg_(97)Zn_1Y_2 alloy with long-period stacking(LPS) structure is lower than that of the commercial AZ91 alloy at room temperature.The microstructure evolutions in Mg_(97)Zn_1Y_2(molar fraction,%) alloys with LPS phase,processed by rolling and annealing the as-cast alloy and rapidly solidifying/melt-spinning and age treating at different temperatures respectively,were investigated by differential thermal analysis(DTA),X-ray diffraction(XRD),and laser optical microscopy(LOM),scanning electron microscopy(SEM),and transmission electron microscopy(TEM).The evolutionary direction of microstructure prescribed by thermodynamics in the Mg_(97)Zn_1Y_2 alloy is reflected from experimental data of the as-cast alloy;and the actual evolution paths selected by kinetics are depicted in detail in the as-spun alloy and rolled alloy.The strong influences of thermodynamic nonequilibrium mechanism,which entails the factual complexity of microstructures typically during rapid solidification and deformation processing for strengthening the creep resistant magnesium alloy,are presented. Mg_ (97) Zn_1Y_2 alloy has been studied as an elevated temperature creep resistant Mg-based alloy for nearly ten years.While, the strength of the cast Mg_ (97) Zn_1Y_2 alloy with long-period stacking (LPS) structure is lower than that of the commercial AZ91 alloy at room temperature. Microstructure evolutions in Mg_ (97) Zn_1Y_2 (molar fraction,%) alloys with LPS phase, processed by rolling and annealing the as-cast alloy and rapidly solidifying / melt-spinning and aging treating at different temperatures respectively, were investigated by differential thermal analysis (DTA), X-ray diffraction (XRD), and laser optical microscopy (LOM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) prescribed by thermodynamics in the Mg_ (97) Zn_1 Y_2 alloy is reflected from experimental data of the as-cast alloy; and the actual evolution paths selected by kinetics are described in detail in the as-spun alloy and rolled alloy. thermodynamic nonequilibrium mechanism, which entails the factual complexity of microstructures typically during rapid solidification and deformation processing for strengthening the creep resistant magnesium alloy, are presented.