In　order　to　describe　the　influence　of　soil　anisotropy　on　stress-strain　relationship,a　non-orthogonal　elastoplastic　constitutive　model　of　transversely　isotropic　clays　is　established　based　on　the　concept　of　the　modified　characteristic　stress.　Modelling　procedures　are　as　follows:(1)　By　referring　to　the　modified　stress　method,the　fabric　tensor　is　introduced　into　the　characteristic　stress　formula　to　incorporate　the　influence　of　anisotropic　fabric.　(2)　Based　on　the　frictional　rule　on　the　octahedral　plane　in　the　modified　characteristic　stress　space,a　transversely　isotropic　β-strength　criterion　reflecting　the　effects　of　soil　anisotropy　and　intermediate　principal　stress　is　established.　(3)　In　the　modified　characteristic　stress　space,the　inclined　yield　surface　is　adopted　to　describe　the　influence　of　the　initial　anisotropic　consolidation　stress　condition　on　the　yield　characteristics　of　soil　by　introducing　the　volumetric　associated　hardening　parameter,and　(4)　the　incremental　direction　of　the　plastic　strain　of　transversely　isotropic　clays　is　determined　by　the　three-dimensional　non-orthogonal　plastic　flow　rule　based　on　the　fractional　partial　derivative.　Only　six　material　parameters　are　needed　in　the　non-orthogonal　elastoplastic　model,which　can　be　determined　by　conventional　triaxial　tests,and　three　model　parameters　are　concerned　in　the　proposed　model,which　can　all　be　easily　determined　by　the　determined　material　parameters.　The　comparison　between　model　predictions　and　experimental　results　shows　that　the　model　can　reasonably　capture　the　strength　and　deformation　properties　of　transversely　isotropic　clays.　©　2020,　Science　Press.　All　right　reserved.