In order to investigate the influences of permeability characteristics of shells and enhance the resoureces utilization efficiency, the effects of different grain sizes of shells on volumetric density, porosity and the permeability coefficient K were discussed with constant head permeability tests on the basis of Darcy's law. The results showed that: In the mixed group, the mixture of shells with different grain sizes induced the increase of the volumetric density and the decrease of porosity due to the fully blend of smaller-sized shells in larger-sized ones; Both the porosity and the permeability coefficient increased, and were proportionally to the general grain size of mixed shells, showing better permeability; The mixture of the different grain sizes on permeability coefficients was noticeable, and the influence of mixing small shells with larger ones on permeability coefficients was more significnat.