Some　samples　of　Al-Si　alloy　with　various　silicon　content　were　treated　by　laser　beam.　The　effects　on　the　structure,　hardness　and　substructure　of　samples　were　investigated.　The　experimental　results　show　that　the　primary　crystal　Al　and　eutectic　silicon　in　the　laser　treated　samples　is　got　thinning　obviously,　the　mosaic　dimension　is　decreased　and　the　dislocation　density　is　increased.　The　laser　melted　zone　of　Al-Si　alloys　increases　with　laser　power　and　silicon　content　increasing,　besides,　the　laser　melted　treatment　can　make　the　surface　hardness　of　Al-Si　alloys　increasing,　and　the　more　the　silicon　content　of　samples,　the　greater　the　hardness　extent.