The problem of the total suction of unsaturated soils is an important branch in the studies of unsaturated soil mechanics. The theory of aqueous film is generally applied to petrochemical and soil sciences. On the basic points

this paper expands the aqueous film scope in the theory to the free water(gravity water) that results from the action of hydrate water

capillary effect and matrix suction. The corresponding disjoining pressure of aqueous films includes matrix suction and capillary action

accordingly; the total suction in unsaturated soils can be expressed as the disjoining pressure of aqueous films. The total suction of unsaturated soils is analyzed in the aspect of their characters using the aqueous film theory; the effect of the aqueous film on the total is then discussed. On this basis

the formula to calculate the total suction is deduced in the significance of the generalized unsaturated soil’s aqueous film theory; and finally

the relationship between the unsaturated soil’s total suction and the saturability when the soil has different sizes is given. The theoretical computation result is well accordant with the real situation

showing that the generalized aqueous theory is of significance to guiding the study of the total suction of unsaturated soils to a certain degree.