The　compound　influence　of　melt　thermal　treatment,　including　melt　mixing　and　melt　superheating,　and　strontium　modification　on　silicon　phases　in　Al-20Si　alloy　was　investigated.　The　results　show　that　with　only　strontium　modification,　the　primary　silicon　in　the　alloy　is　modified　weakly,　and　the　morphology　change　of　the　eutectic　silicon　can　be　ignored.　The　low　temperature　Sr　modified　Al-10Si　melt　mixed　with　the　high　temperature　Al-30Si　melt　in　the　ratio　of　1:1,　nuclei　number　in　Al-20Si　melt　is　increased,　resulting　in　the　significant　refinement　of　primary　Si　phase.　And　then,　mixed　melt　is　treated　by　superheating　to　1000°C,　and　the　average　size　of　the　primary　silicon　is　decreased　to　approximately　14　μm,　and　the　morphology　of　the　eutectic　silicon　is　changed　from　long　needle-shape　into　short　fiber-like.