Effects　of　the　melt　thermal　treatment　with　composition　compensation　on　morphology　of　primary　Si　in　hypereutectic　A1-20Si　alloy　were　investigated.　The　results　show　that　the　technology　can　refine　grain　size　of　primary　Si　to　approximately　36　μm　within　100　min,　exhibiting　an　obvious　modification　effect　on　the　primary　Si　and　a　long　duration　time.　So　the　melt　thermal　treatment　with　composition　compensation　is　a　simply　and　practical　technology　for　modifying　the　primary　Si　in　the　A1-20Si　alloy　without　modifier　addition.