This　paper　investigates　the　laws　of　Ca　microalloying　on　the　microstructure　and　mechanical　properties　of　as-cast　and　multi-direction　forged　Mg-8Gd-1Er-1Zn-0.5Zr-xCa　(x=0.1,　0.3,　0.5,　mass　fraction,　%)　alloys.　The　results　show　that,　with　the　increase　of　Ca　content,　the　second　phase　transformation　process　of　the　alloy　is　as　follows:　discontinuous　fishbone　Mg3Gd　phase→coarsened　Mg3Gd　phase+Mg5Gd　phase+Mg2Ca　phase→small　amount　of　Mg3Gd　phase+Mg5Gd　phase+Mg2Ca　phase+massive　LPSO　phase,　the　grain　size　of　the　alloy　decreases,　the　volume　fraction　of　the　second　phase　increases,　and　the　mechanical　properties　improve.　The　alloy　with　0.5%　Ca　addition　has　the　highest　tensile　strength　(TS),　yield　strength　(YS)　and　elongation　(EL)　of　241.0　MPa,　149.2　MPa　and　5.7%,　respectively.　LPSO　phase　forms　at　grain　boundaries　after　solid　solution　treatment,　and　its　volume　fraction　increases　with　the　increase　of　Ca　content,　that　promotes　the　dynamic　recrystallization　of　the　alloy　during　the　subsequent　forging　process,　the　increase　of　basal　weave　strength　and　the　decrease　of　basal　Schmid　factor.　The　best　mechanical　properties　of　the　alloy　after　forging　are　achieved　when　the　Ca　content　is　0.5%,　the　TS,　YS　and　EL　of　the　alloy　reach　344.6　MPa,　274.5　MPa　and　8.1%,　respectively.　The　analysis　results　conclude　that　the　basal　weave　enhancement　and　grain　boundary　strengthening　are　the　main　reasons　for　the　improved　mechanical　properties　of　the　forged　state　alloy.　©　2023　Central　South　University　of　Technology.　All　rights　reserved.