The　effects　of　increasing　levels　of　Si　on　the　microstructure　and　damping　capacities　of　Mg-Al-Si　alloys　were　investigated.　The　results　show　that　the　morphology　of　the　Mg2Si　phase　is　found　to　be　a　function　of　the　Si　content.　The　Mg2Si　particles　with　up　to　1.3　%　of　mass　fractions　of　Si　have　a　Chinese-script　morphology　and　dendritic　Mg2Si　crystals　were　precipitated　predominantly　inside　the　grains　of　a　2.3　%　of　mass　fractions　of　Si-containing　alloy.　The　morphology　and　volume　of　the　Mg2Si　phase　as　well　as　the　distribution　of　the　Mg17Al12　eutectic　have　a　significant　effect　on　the　damping　capacity　of　the　alloy.　With　a　low　strain　amplitude,　the　dislocation　density　increases　with　the　formation　of　Mg2Si　particles,　improving　the　damping　property,　while　in　the　high-strain　region,　dispersed　Mg17Al12　precipitates　and　coarse　Mg2Si　particles　lead　to　a　reduction　of　the　internal　friction.