The　effect　of　solution　treatment　at　420　degrees　C　on　the　microstructures　and　mechanical　properties　of　the　Mg-6Al-Zn+xSn　(x=0.5,　1,　2　and　3.5　mass　%)　alloys　have　been　investigated.　The　results　showed　that　the　Mg2Sn　phase　was　present　in　both　the　cast　and　the　heat-treated　alloys.　The　Mg2Sn　particles　tended　to　be　spherodized　during　the　solution　treatment.　Amount　of　Sn　increased　the　tensile　strength　of　the　alloys.