The invention relates to a method for preparing an icosahedral quasicrystalline phase and long-period stacking ordered structure combined reinforced Mg-Zn-
Y alloy. The 
alloy prepared by the method contains the chemical elements in percentage by 
mass: 10wt% of Zn and Y and the balance of Mg, wherein Zn is added in the form of pure Zn, Y is added in the form of Mg-25wt%Y intermediate 
alloy, and Mg is industrial pure 
magnesium. According to the method, 
alloy structures, obtained after 
magnesium alloy is subjected to 
smelting, 
metal type molding and 
solid solution and grading aging treatment, are an alpha-Mg 
solid solution, an icosahedral quasicrystalline phase and a long-period stacking ordered structure phase; a quasi-
crystal, which is formed through dispersion 
precipitation, depends on strong pinning on 
dislocation and forms a firm interface with a matrix, so that the 
magnesium alloy can be remarkably reinforced; a long-period structure and a matrix interface are in coherency, so that the 
thermal stability is very high, the coarsening is not easy, the 
dislocation motion and the extension of deformation twin crystals can be remarkably hindered, the mechanical properties of the alloy are improved obviously, the tensile strength can reach 352MPa to the maximum, and the elongation percentage can reach 7.5%. The method is beneficial to the promotion of the extensive application of high-strength 
magnesium alloy in many fields, such as automobiles, 
aviation and 
electronic communication.