In　order　to　improve　the　meshing　performance　of　non-orthogonal　helical　face-gears,　a　designation　of　double-crowned　tooth　modification　with　high-order　transmission　error　(HTE)　is　constructed　in　this　paper.　First,　the　double-crowned　tooth　modification　is　designed　based　on　the　tooth　profile　modification　of　the　rack-cutter　and　the　motion　relationship　between　the　rack-cutter　and　the　processed　pinion,　and　then,　the　designation　of　high-order　tooth　modification　is　verified　by　using　tooth　contact　analysis　(TCA).　Second,　a　parameterized　3D　grid　of　modified　gears　is　generated　based　on　MATLAB　programming,　and　a　simulation　of　loaded　tooth　contact　analysis　for　modified　non-orthogonal　helical　face-gears　is　carried　out　by　using　ABAQUS　software.　Third,　the　calculation　results　of　the　standard　tooth,　second-order　parabolic　modified　tooth　and　high-order　parabolic　modified　tooth　are　compared　with　and　without　the　assembly　errors.　Ultimately,　an　example　is　presented　and　the　results　show　that　the　geometric　transmission　error　of　the　newly　designed　high-order　modified　non-orthogonal　helical　face-gears　conforms　to　the　expected　design.　Compared　with　the　second-order　parabolic　tooth　modification,　the　newly　designed　high-order　tooth　modification　pair　shows　a　better　meshing　performance　with　and　without　assembly　errors.　The　research　of　this　paper　can　provide　ideas　and　methods　for　the　tooth　modification　design　of　non-orthogonal　helical　face-gear.　©　2023,　The　Author(s),　under　exclusive　license　to　Springer　Nature　Singapore　Pte　Ltd.