The　active　mechanisms　of　rare　earth　element　erbium　(Er)　in　part　of　aluminum　alloys　were　investigated.　Based　on　the　investigation　of　the　effect　of　the　unitary　rare　earth　elements　(Er,　La,　Y,　Ce,　Nd,　Gd,　and　Sc)　and　the　transition　element　zirconium　on　the　aluminum　alloys,　it　is　concluded　that,　with　Er　alloyed,　high　purity　aluminum　and　Al-Mg　alloys　are　featured　with　refined　grain　structure,　superior　heat　stability　and　even　higher　hardness　or　tensile　strength　with　unchanged　ductility;　but　Er　is　not　beneficial　to　the　mechanical　property　of　Al-Cu　alloy,　so　is　Sc.　It　may　also　be　concluded,　to　most　of　the　aluminum　alloys,　Er　can　be　an　effective　alloying　element,　like　Sc;　and　for　the　lower　price　of　Er,　the　cost　of　modifying　aluminum　alloys　by　Er　will　be　reduced.