A high-strength high-modulus
magnesium alloy comprises 3-20% of alloying element and the balance of
magnesium substrate, wherein the alloying element comprises heavy
rare earth,
silicon and / or
germanium, and
tin and / or
antimony and / or
zinc; Si and Ge as well as Sn, Sb and Zn can be simultaneously added and can also be added individually; and the heavy
rare earth is selected from at least one of
gadolinium,
dysprosium,
terbium,
holmium erbium,
thulium,
ytterbium and
lutetium. The preparation method comprises the steps of: heating and melting pure
magnesium in protective
atmosphere, adding pure
silicon to the pure magnesium melt, stirring, dissolving, heating-up to 20-30 DEG C, sequentially adding an interalloy of the other components, stirring, controlling the interalloy to be completely molten until the
casting time is less than or equal to 4min, and
casting to obtain a cast
ingot. The high-strength high-modulus
magnesium alloy is reasonable in component proportioning, and easy to process and manufacture; and the prepared high-strength high-modulus
magnesium alloy has high room-temperature strength and elasticity modulus and better
plasticity, and comprehensive performances apparently higher than those of the existing magnesium-
rare earth, and is suitable for industrial production.