A　combination　of　high　resolution　transmission　electron　microscopy　(HRTEM)　and　electron　backscatter　diffraction　(EBSD)　was　applied　to　study　the　formation　mechanism　associated　with　high　index　twins　in　a　deformed　magnesium　alloy.　Utilizing　the　information　obtained　about　the　formation　of　high　index　twins　by　identifying　their　structural　characteristics　and　interfacial　atomic　arrangement,　we　found　that　high　index　twins　were　obtained　from　dislocation-modified　double　twins.　With　increasing　deformation,　misorientations　between　the　matrix　and　deformation　twin　increased,　resulting　in　the　evolution　of　double　twins　into　a　variety　of　structures.　This　discovery　about　high　index　twin　formation　can　greatly　improve　the　ability　to　identify　various　types　of　double　twins　in　EBSD　data.　This　mechanism　provides　a　new　insight　into　the　formation　of　high　index　twins　and　aids　in　understanding　the　material　fractures　caused　by　double　twinning.　(C)　2019　Elsevier　B.V.　All　rights　reserved.