This paper analyses the optimigation compositions of hypereutectic Al-Si alloys for pistons,according to the specific property of hypsreutectic Al-Si alloys. The compound salt modifier of development and production with phospho-sulphur can be used to batch process. This kind of modifier can refine not only the crystals of primary silicon but also the eutectic sillicon, and the effective period can last 3 hours. The properties of the alloys have surpassed the requirement of the state standard "GB1148-82". Now, it has been used to batch process.