The　effect　of　trace　element　Er　on　the　microstructure　and　properties　of　Al-6Mg-0.7Mn-0.1Cr-0.15Ti　alloy　was　investigated.　The　results　show　that　the　ultimate　room-temperature　and　high-temperature　strength　sof　the　alloy　have　not　increased　obviously　with　the　addition　of　erbium,　but　the　uniform　elongation　of　alloys　decreases　from　9%　and　27.5%　to　5.5%　and　22.5%,　respectively.　The　reason　is　that　the　addition　of　Er　will　first　react　with　Ti,　Cr　to　form　Al20Ti2Er,　Al8Cr4Er　phases.　The　precipitation　strengthening　makes　up　the　weakening　of　grain　refinement　strengthening.　During　deformation,　the　primary　Al(TiCr)Er　and　Al3Er　particles　fracture　first　and　act　as　the　microcrack　sources　because　of　the　stress　concentration.