Numerical simulation test is a powerful supplement of indoor and on-site tests of coarse granular material, which does not require much manpower and resources, and isnt limited by time and space, and it is the most important that the size of the sample is not limited and the boundary conditions could be controlled. In order to construct a numerical simulation test model, the authors study a two-dimensional random particle-generating algorithm of coarse granular materials. First, loosely distributed particles are randomly generated according to the gradation curve. Then, the packing and distribution pattern of these particles in a test tube under gravity is simulated adopting DDA(discontinuous deformation analysis). Lastly, they form stably-structured aggregates that contact each other. This result provides a sound basis for mechanics simu lation test of coarse granular material.