The　strength　characteristic　of　the　transverse　isotropic　soil　include　two　aspects.　On　one　hand,　the　strength　curves　are　not　symmetric　around　the　three　principal　stress　axes　on　deviatoric　plane.　On　the　other　hand,　the　strength　parameter　varies　with　the　included　angle　δ　between　the　acting　plane　of　the　major　principal　stress　and　the　depositional　plane.　The　existing　studies　about　the　strength　of　transverse　isotropic　materials　are　immature,　especially　the　strength　description　of　the　included　angle　δ　direction.　The　concept　of　mobilized　plane　is　introduced　into　a　method　that　considers　the　microstructural　tensor.　Based　on　the　coincidence　of　the　stress　space　with　the　physical　space,　the　relative　position　between　the　3D　mobilized　plane　and　the　depositional　plane　is　analyzed.　Then　a　3D　strength　parameter　ηn　is　proposed　by　considering　the　change　rules　of　included　angle　δ　direction.　The　transverse　isotropic　strength　criterion　is　proposed　by　marrying　the　3D　strength　parameter　to　the　Matsuoka-Nakai　strength　criterion.　The　proposed　transverse　isotropic　strength　criterion　is　able　to　describe　the　distortion　of　the　strength　curves　on　deviatoric　plane　and　the　non-monotonic　rule　with　respect　to　the　included　angle　δ　comprehensively.　©　2018,　Editorial　Office　of　Chinese　Journal　of　Geotechnical　Engineering.　All　right　reserved.