This thesis focuses on numerical modeling of granular materials with discrete and continuum methods. The links between both methods are discussed. Discrete element methodis taken as an example of discrete method. For the continuum method, hypoplastic model and micropolar theory are used. The discrete element method (DEM) is used to simulate several element tests for granular materials, including simple shear test and biaxialcompression test with different boundary conditions. Using averaging methods, stress, strain and rotation in DEM simulations are discussed. Based on hypoplastic model and micropolar theory, a new constitutive model is developed with complex formulations. The resulting model represents relationships between the stress-strain variables and the moment-curvature variables and is much simpler than the existing micropolar hypoplastic model.The only additional material parameter is the characteristic length, which can be determined from the width of shear band. This new model is implemented in the finite element program ABAQUS. Biaxial tests, periodic shear tests and simple shear tests are simulated. By using different internal lengths, size dependent material behavior is well captured. The results of continuum simulations with FEM are compared with experiments and DEM simulations.