The　difference　of　the　electron　chemical　potential　energy　between　the　atom　cells　in　the　calculated　aluminum　alloys　was　considered　to　have　a　negative　effect　on　the　formation　energy　of　the　alloy　system.　The　function　of　parameter　ψ*　to　the　thermodynamic　calculation　was　assessed　and　a　new　formula　about　the　parameter　ψ*　for　rare　earth　elements　were　established.　The　results　show　that　the　calculated　value　through　the　proposal　parameter　ψ*　is　near　to　the　system　work　function,　and　the　maximum　relative　error　is　within　12.0%　while　the　average　relative　error　is　less　than　5.0%.　The　calculated　mixing　enthalpy　values　of　the　alloys　are　much　closer　to　the　published　experimental　results.