Effects　of　trace　Er　and　Mn　on　the　microstructures　and　mechanical　properties　of　as-cast,　homogenized,　hot-rolled　and　cold-rolled　alloys　were　investigated.　Their　existing　forms　and　interactions　with　each　other　were　studied.　The　results　showed　that　the　element　erbium　and　manganese　had　good　effect　on　improving　the　Al-Mg　alloy　mechanical　properties,　but　the　strengthening　effect　would　be　weakened　when　they　were　added　together,　and　influenced　the　function　of　individual　element.