The　effects　of　the　heat　treatment　process　parameters　on　the　microstructure　and　mechanical　properties　of　a　selective　laser　melted　(SLMed)　AlSi10Mg　alloy　were　systematically　investigated.　The　SLMed　AlSi10Mg　alloy　was　treated　with　T1　(180°C×　4h　+　air　cooling)　process,　which　had　the　microstructure　of　fine　α-Al　grains,　fine　Si　phase,　and　nano-sized　precipitations.　The　microhardness　significantly　increased　to　150　HV,　which　is　even　higher　than　as-SLMed　one　(126　HV).　The　microhardness　of　SLMed　AlSi10Mg　alloy　treated　with　T4　(540°C　×　2h　+　water　cooling)　heat-treatment　process　significantly　decreased　to　62　HV　due　to　the　growth　of　α-Al　grains,　Si　phase　and　the　formation　of　β-AlFeSi　phase.　However,　the　microhardness　and　ultimate　tensile　strength　of　AlSi10Mg　alloy　treated　with　T6　(540°C　×　2　h　water　cool　+　180°C　×　4　h　air　cool)　process　decreased　to　91　HV,　although　the　strengthening　precipitation　of　Mg2Si　phase　formed.　It　indicates　that　the　Mg2Si　phase　cannot　compensate　for　the　adverse　effect　of　grain　growth.　It　may　provide　the　best　potential　heat　treatment　method　for　fabricating　the　high　strength　SLMed　AlSi10Mg　alloy.　©　2021　Trans　Tech　Publications　Ltd,　Switzerland.