The　change　of　twinning　morphology　plays　an　important　role　in　the　modification　of　Al-Si　alloys,　which　are　widely　used　in　industrial　applications.　However,　the　interpretation　of　this　change　is　still　insufficient.　In　this　work,　the　microstructure　of　twins　was　investigated　in　two　kinds　of　Al-Si　alloys　with　different　additions　of　Ba　using　high-resolution　transmission　electron　microscopy　(HRTEM).　Unlike　the　normal　{111}　twin　that　exists　in　Ba-free　alloy,　discontinuous　twins　and　multiple　twins　were　observed　in　the　Ba-containing　alloy.　In　addition,　the　9R　structure　formed　by　the　dissociation　of　twins　was　firstly　observed　at　the　turning　of　discontinuous　twins　and　the　intersection　of　multiple　twins　in　Al-Si　alloys.