Abstract: The mechanical properties and characteristics of sand are significantly affected by particle shape. This paper is mainly aimed to quantify and build the grain shape. A new method based on ODEC (overlapping discrete element cluster) method is proposed. Firstly, the two-dimensional roundness of a particle in three projection planes is extracted through photography, and the weighted average roundness is calculated. Then the weighted average roundness is employed of particles to generate particles with various irregular shapes in numerical model through Matlab code and clump block function of PFC^3D.