High-strength antirusting Mg-Al-Mn die-casting magnesium alloy containing yttrium-rich rare earth

The invention relates to a high-strength erosion-resistant die cast magnesium alloy containing yttrium-rich rare earth. The alloy is prepared by 97% to 91% by mass percentage of AM60 magnesium alloy and 3% to 9% by mass percentage of magnesium- yttrium-rich interalloy; the magnesium- yttrium-rich interalloy is prepared by 80% by mass percentage of magnesium and 20% by mass percentage of special yttrium-rich rare earth; the special yttrium-rich rare earth is the residual cheap yttrium-rich rare earth after Eu, Dy, Tb and Lu high-valence elements is extracted from common yttrium-rich rare earth; by adding some special yttrium-rich mixing rare earth to AM60 alloy, the high plasticity of the alloy is maintained, the strength and corrosion resistance is improved, the comprehensive performance is obviously enhanced compared with AM60 magnesium alloy.