The　crystal　structures,　stability,　mechanical　behaviors,　thermodynamic　properties　and　electronic　structures　of　Al2Si2La　and　Al2Si2Pr　compounds　have　been　investigated　by　means　of　first-principles　calculations.　It　is　revealed　from　formation　enthalpies　that　Al2Si2La　exhibit　much　more　thermodynamically　stability.　According　to　the　results　of　elastic　constants,　Al2Si2Pr　has　stronger　incompressibility,　stronger　shape　deformation　resistance　and　higher　stiffness.　It　can　be　concluded　from　Debye　temperature　and　minimum　thermal　conductivity　that　Al2Si2Pr　and　Al2Si2La　exhibit　nearly　the　same　thermal　conductivity.　Electronic　structures　results　demonstrate　that　the　Al-Si　bonds　in　Al2Si2La　and　Al2Si2Pr　are　attributed　to　the　hybridization　of　Al　3s　state,　Al　3p　state　and　Si　3p　state,　while　RE-Si　bonds　are　the　contribution　of　Si　3p　state　and　La　5d　or　Pr　4f　state　in　Al2Si2La　and　Al2Si2Pr,　respectively.