Physically　parallel　to　ferroelectric　morphotropic　phase　boundary,　a　phase　boundary　separating　two　ferromagnetic　phases　of　different　crystallographic　symmetries　was　experimentally　found　in　TbxDy1-xCo2　via　high-resolution　synchrotron　X-ray　diffraction.　However,　lack　of　the　theoretical　support　makes　the　morphotropic　phase　boundary　in　ferromagnetic　system　debatable.　Here,　a　first-principle　calculation　was　employed　to　investigate　the　electronic　structure　variation　during　the　morphotropic　phase　transition　in　TbxDy1-xCo2.　It　offers　a　theoretical　basis　for　the　ferromagnetic　phase　of　different　crystallographic　symmetries　in　TbxDy1-xCo2.　It　also　provides　an　explanation　for　why　morphotropic　phase　boundary　occurs　in　TbxDy1-xCo2　alloys　and　offers　a　serviceable　method　to　search　for　the　morphotropic　phase　boundary　phenomena　in　other　alloys　via　computational　rather　than　experimental　method.　(C)　2016　Published　by　Elsevier　B.V.