The　effect　of　annealing　on　the　mechanical　properties,　intergranular　corrosion　(IGC)　properties,　and　microstructure　of　Al–Mg–Zn　alloys　is　studied.　The　results　show　that　with　the　increase　of　annealing　temperature,　the　strength　of　the　alloy　decreases,　the　elongation　increases,　and　the　corrosion　resistance　firstly　increases　and　then　decreases.　The　alloy　exhibits　a　high　corrosion　resistance　and　good　mechanical　properties　when　the　annealing　treatment　is　270　°C　for　2　h.　Meanwhile,　the　IGC　mass　loss　value　is　less　than　15　mg　cm−2.　In　addition,　the　ultimate　tensile　strength,　yield　strength,　and　elongation　are　416,　250　MPa,　and　16.0%,　respectively.　The　T-Mg32(Al,　Zn)49　phases　are　directly　precipitated　when　annealing　at　270　°C　for　2　h.　After　sensitization,　T　phase　gradually　grows　and　coarsens.　When　the　alloy　is　annealing　at　400　°C　for　2　h,　a　part　of　T　phase　gradually　dissolves　in　the　Al　matrix.　After　sensitization,　the　Mg　atoms　with　higher　supersaturation　gradually　diffuse　to　grain　boundary　by　bulk　diffusion　due　to　the　low　dislocation　density　and　form　a　thin　precipitate　film,　which　deteriorates　the　corrosion　resistance　of　the　alloy.　The　details　of　corrosion　mechanism　analysis　are　as　follows.　©　2024　Wiley-VCH　GmbH.