Abstract: An anisotropic elastoplastic constitutive relation based on the microstructure tensor theory is proposed. The microstructure tensor is introduced to describe the spatial distribution function of the strength parameters of transversely isotropic materials. The user defined model is developed in FLAC^3D, and the triaxial numerical simulation tests on columnar jointed specimen with a joint angle of 75° are carried out. The simulated results are in good agreement with the experimental ones, indicating the feasibility of the model. The developed constitutive model is also applied to the numerical simulation calculation of the excavation of the foundation of Baihetan high dam. The results show that the deformation characteristics of the anisotropic model are closer to the actual monitoring results than thoes of the isotropic model. The results can provide theoretical support for the construction of Baihetan Hydropower Station.