The　effect　of　the　alloying　elements　Cu　and　Mg,　the　solution　and　artificial　aging　process　on　the　microstructure　and　property　were　investigated.　Solution　treatment　was　carried　out　at　535　±　5°C　in　different　time　for　the　Al-Si-Cu-Mg　casting　alloy,　and　the　artificial　aging　was　carried　out　at　160　±　5°C　and　175　±　5°C　and190　±　5°C　in　different　time.　The　microstructure　has　been　investigated　by　Optical　Microscopy,　Scanning　Electron　Microscopy　(SEM).　We　found　that　most　of　Cu　and　Mg　element　in　the　alloy　gathered　and　formed　multivariate　composite　phase　at　grain　boundaries.　With　the　increasing　of　solid　solution　time,　the　intermetallic　phases　will　be　dissolution　into　the　matrix,　and　if　the　solid　solution　time　is　long　enough,　they　will　be　distributed　uniformly　in　alloy.　With　the　increase　of　the　aging　temperature,　the　time　for　aging　peak　will　be　shorter,　but　the　peak　will　be　lower.　Finally,　we　determine　the　optimum　heat　treatment　process　is　535°C　×　12h　+　175°C　×　8h.　©　(2014)　Trans　Tech　Publications,　Switzerland.