Abstract: Normal test method is employed to explore the relationship between dry density and optimum water content of coal gangue used in darning. The results show that the compaction will change the distribution of grain size, the particle size distribution will be more satisfactory and get a higher degree of consolidation. When the content of coarse grain is great than 60 %, the crush degree is observably increasing. When the content of coarse grain is less; than 40 %, the leading engineering characteristic of coal gangue is determined by fine grain. The coefficient of permeability of coal gangue can be defined as an exponential expression of void ratio. With tbe increasing of fine grain, tbe penetrability of coal gangue will be clearly lower.