Works by many persons indicated that it was extremely difficult to find the shear strength-dry density-water content relation directly, so a wise approach is to find an equivalent, for shear strength with a prerequisite that it's easier to determine the correlation among this equivalent, dry density and water content. By means of rate process theory, Mitchell etc. found that there is an unique linear relationship between shear strength and number of interparticle bonds, and this relationship doesn't change with soil type, consolidation condition, density and water content. As a result, number of interparticle bonds is an equivalent of shear strength. However, it is a pity that correlation among number of bonds, dry density and water content is still not known, so looking for another equivalent is necessary.