Haphazard packing of equal and unequal spheres can be performed for the spheres of zeo-litic material with a density of 1.80. The packing of such spheres in air is equivalent to the packing of natural grains in water. Packing concentrations of equal spheres are obtained for different packing intensities. Unequal spheres can be regarded as equal ones in a wide range of diameter ratio, so far as the packing concentration is concerned. A threshold of diameter ratio exists at 0.70, below which the packing concentration begin to increase. The variation curves of concentration vs. diameter ratio are obtained in the experiment. The result will be helpful for understanding the sedimentary process and the concentrations of voids in sedimentary rocks.