Abstract：Through experimental results on the compaction breakage of loose rock blocks，some breaking laws are obtained. The results show that the majority of blocks are broken before the relative load reaches 0.5 or 0.6 compared to unixial compressive strength. When the stress exceeds such level，the broken rate of blocks is very small. Therefore，the grading of granular tends to keep constant even if the exerted load is increased. For soft rock，e.g.，coal，the ultimate fine particles have a greater percentage. However，for hard rock，e.g.，sand stone，the difference of ingredient of each class of particle is not apparent. For rock blocks with different strengths，the curves of grading of granular have strong similarity and relativity and can be described by polynomial.
