Selective Laser Sintering (SLS) is an efficient and rapid manufacturing technique because it allows for making complex parts that are often unobtainable by traditional manufacturing processes. However, the application of such technique is quite limited by the balling phenomenon, for which it largely reduces the manufacturing quality. Eliminating the structural defects is crucial to overcome the balling phenomenon. Therefore, a better understanding of the packing structure details is urgently needed for the SLS applications. In this study, the sequential addition packing algorithm is employed to investigate the random packing of spherical particles with and without shaking effect. The 3-D random packing structures are demonstrated by illustrative pictures and quantified in terms of pair distribution function, coordination number and packing density. The results are presented and discussed aiming to produce the optimal packing parameters for the SLS manufacturing process.