Abstract: 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 η _n 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.