Abstract: The absence of complementary shear stress on the side boundary of a specimen in the simple shear tests will cause stress inhomogeneity. An enhanced critical state-based constitutive model is proposed by incorporating the inherent anisotropy fabric, and also implemented into the finite element code for the numerical simulation. In addition, a three-dimensional finite element analysis with the same size as the GDS-type simple shear apparatus is performed to illustrate the inhomogeneous features of the specimen. Above all, this study can improve the understanding and knowledge of boundary effects for the simple shear tests, and provide a calculation method for analyzing the inhomogeneous ness of the specimen.