Spark-Plasma Sintering (SPS) involves rapid heating of powder by electric current with simultaneous application of external pressure. Numerous experimental investigations point to the ability of SPS to render highly-dense powder products with the potential of grain size retention. The latter ability is of significance for the consolidation of nano-powder materials where the grain growth is one of the major problems. A model for spark-plasma sintering taking into consideration various mechanisms of material transport is developed. The results of modeling agree satisfactorily with the experimental data in terms of SPS shrinkage kinetics.