Abstract: The anisotropy of the material refers to the differences in mechanical parameters, structural characteristics and stress-strain relationships of different directions. Establishment of proper strength criteria and reasonable constitutive models which can accurately illustrate this complex characteristic of materials is a huge contribution to the theoretical studies of constitutive relations of materials. However, the anisotropy of materials has always been a major difficulty for researchers in determining the mechanical properties of materials. In order to demonstrate the abstract affection of the materials’ anisotropy, professor Quanshui Zheng proposed the isotropicization theorem, providing valuable thoughts and referential ideas for subsequent researchers to deal with the anisotropy problem. Building on these ideas, the authors proposed the transformed stress (TS) method. The TS method focused on the stress-induced anisotropy of granular geotechnical materials, introduced another train of thought to describe the anisotropy of materials. The TS method followed the theory of professor Zheng about isotopicizing the anisotropy of the materials, which can be considered as a development of the isotropicization theorem. The aim of this article is to clarify the internal connection between the isotropicization theorem and the transformed stress method through the analysis of the deduction progress of transformed stress method. Also, the practical problems faced in the anisotropy treatment process of specific materials and how these problems can be solved with TS method was illustrated with an example of the stress-induced anisotropy treatment of soil materials. In this paper, three reasonable assumptions in practical application of the TS method have been raised, and the specific stress transformation formula is deduced. Also, the significance of applying the TS method even when knowing the specific functions considering the anisotropy of geotechnical materials has been delivered, and the necessity of application of TS method in the progress of constructing soil elastic-plastic constitutive models has also been proved.