Despite　studies　on　the　formation　and　structural　features　of　deformation　twins　of　general　types　were　reported　extensively　on　Mg　alloys,　the　available　information　for　understanding　structural　natures　of　unusual　twins　which　could　exhibit　twin-like　symmetry　with　respect　to　a　high-index　plane　was　still　quite　lacking　so　far.　In　this　work,　the　Mg-Y1.1-Nd0.4-Zn0.8　alloy　(%,　atom　fraction)　subjected　to　compression　to　a　strain　of　10%　at　room　temperature　was　structurally　characterized　by　means　of　transmission　electron　microscopy　(TEM).　A　kind　of　uncommon　deformation　twin　band　of　{1015}　high-index　type　was　found　to　form　after　the　alloy　being　compressed　to　a　strain　of　10%.　TEM　images　showed　that　the　twin　interface　of　this　twin　band　was　not　along　the　{1015}　plane　which　was　theoretically　required　for　the　{1015}　twinning,　but　was　actually　nearly　parallel　with　{1011}　plane　of　the　matrix.　Inside　the　{1015}　twin　band,　secondary　twinning　substructure　and　clear　evidence　associated　with　the　occurrence　of　a　small　angle　of　lattice　reorientation　could　also　be　observed.　It　followed　that　the　formation　of　the　{1015}　twin　band　could　be　attributed　to　a　double　twinning　process,　during　which　necessary　accommodation　of　small　angle　of　lattice　rotation　should　be　involved.　Based　on　this　formation　mechanism　along　with　analysis　of　crystallographic　twinning　geometry,　other　possible　twin　bands　of　{1016},　{2021},　{3031}　and　{3032}　types　could　be　predicted　for　Mg　alloys.　These　twin　bands　of　high-index　types　could　be　regarded　as　a　type　of　apparent　twinning　band,　whose　morphological　characteristics　and　their　boundary　orientation　should　be　similar　to　those　of　their　corresponding　primary　twinning　bands.　©　Editorial　Office　of　Chinese　Journal　of　Rare　Metals.　All　right　reserved.