The　effects　of　the　homogenization　conditions　on　the　microstructure　of　Al-Zn-Mg-Cu-Zr-0.5Er　alloy　were　investigated　by　differential　scanning　calorimetry　(DSC),　optical　microscopy　(OM),　scanning　electron　microscopy　(SEM),　energy　dispersive　spectrometry　(EDS),　and　X-ray　diffraction　(XRD).　The　results　showed　that　a　lot　of　coarse　phases　existed　in　as-cast　Al-Zn-Mg-Cu-Zr-0.5Er　alloy.　The　dissolvable　phases　at　grain　boundary　consisted　of　Mg32　(Al,　Zn)49.　The　residual　phases　dissolved　into　the　matrix　gradually　during　homogenization　with　increasing　temperature　and　prolonging　holding　time.　When　the　temperature　increased　to　465°C,　and　time　prolongs　to　24h,　the　main　phase　disappeared　except　the　Fe　and　Er　enriched　phase,　as　a　result　of　its　high　melting　temperature.　Taking　into　account　the　precipitation　of　Al3Er,　we　used　a　two-step　homogenization.　Hence,　the　optimum　parameters　of　homogenization　were　400　°C　for　4　h　and　465　°C　for　24　h,　which　are　good　for　the　presence　of　coherent,　elastically　hard　and　nano-sized　Al3(Er,　Zr)　particles　and　the　dissolvable　coarse　phases.　©　(2015)　Trans　Tech　Publications,　Switzerland.