A series of triaxial undrained shear tests is conducted on the granular assemblies using discrete element method. The effects of initial fabric anisotropy caused by different sample preparation methods on the mechanical behavior and critical state of granular soil are investigated. The numerical samples are generated using the radius expansion method and the gravity deposition method

which can produce the samples with initial isotropic and anisotropic fabrics respectively. The fabric tensor is used to quantify the fabric anisotropy of granular soil and the influences of different initial fabric anisotropies on the fabric evolution are presented. The results show that initial fabric anisotropy has a great impact on the dilatancy of granular soil. The dilatancy of granular soil is more significant when the samples are more anisotropic or the direction of fabric anisotropy and loading direction are coincided. It is also observed that initial fabric anisotropy has no influence on the critical state of granular soil and the critical fabric tensor has a unique measure associated with the loading mode.