The function of modification and refinement of a master alloy Al-Ti-Sr solidified at cooling rates of 10 Ks(-1) or less and 10(3) Ks(-1) or greater for a hypoeutectic Al-10 wt% Si alloy has been studied. The master alloy Al-Ti-Sr solidified at a cooling rate of 10(3) Ks(-1) or greater presents a more marked function of modification and refinement than that solidified at a cooling rate of 10 Ks(-1) or less, both under the casting condition of a sand mould and a permanent mould. The addition amount of the master alloy is reduced by rapid solidification technology, keeping the same degree of modification and refinement.