In　order　to　improve　the　properties　of　the　brazing　alloy　Al-7Si-20Cu,　a　small　amount　of　rare　earth　(RE)　Er　was　added　into　Al-7Si-20Cu　brazing　alloy　aiming　at　examining　the　effect　of　different　amounts　of　Er　on　the　physical　properties,　spreading　property　and　mechanical　properties　of　the　solders.　Results　show　that　a　small　amount　of　Er　has　no　obvious　effect　on　the　melting　temperature　of　Al-Si-Cu　solder　alloy,　but　can　notably　improve　spreading　property　of　brazing　alloy　on　LF21　surface,　especially　when　the　content　of　Er　is　Within　0.05-0.1%.　According　to　the　examination　on　the　microstructure　of　AlSiCu　brazing　alloy,　with　the　increase　of　Er　content　the　microstructure　becomes　finer　and　the　length　of　acicular　eutectic　Silicon　is　shortening.