To improve the strength-toughness and heat-resistance of die cast magnesium alloy, the ZA85 alloy has been prepared by adding proper amount of spherical quasicrystals containing master alloy. The results indicate that the solidification microstructure is inlaid with quasicrystal particles, which is a new phase i(Mg45Zn47Y5Mn3), co-existing with the α-Mg, Φ(Al2Mg5Zn2) phase and τ(Mg32(AlZn)49) phase. Mechanical properties of ZA85 alloys have been dramatically improved owing to the obvious grain refinement of the matrix microstructure. While adding 1.7 wt % spherical quasicrystal containing master alloy, macro-hardness of ZA85 magnesium alloy reaches 75HB; meanwhile, impact toughness reaches the peak value 18.4Jcm-2, which is about 202% of ZA85 base alloy. Due to the pinning effect of quasicrystal particles on grain boundaries, the strengthened ZA85 alloys would have excellent heat-resistance.