Abstract: Numerical simulation of two-dimensional assembly of disks was carried out based on discrete element method(DEM) where the non-linear contact relationship between particles was considered.Each particle was located by a node at its centre and the plastic indentation of the contacts between neighboring particles was represented by a non-linear spring.The local fabric evolution(void number,the valence and the coordination number) and macroscopic mechanical behavior were investigated under quasi-static biaxial loading at small deformation.By making a link between the discrete force system and its continuum equivalent,macroscopic average stress in the granular assembly could be derived.The macrocosmic stress-strain relationships under different circumstances were presented and loading-unloading cycle could be reproduced by DEM.The effect of friction coefficient between particles on the intensity was compared and discussed.It was shown that the microscopic parameters of granular materials affected greatly the macroscopic response of the granular materials.