Large-scale triaxial tests on metamorphic soft rock embankment filler at Ankang west section of Shiyan-Tianshui expressway are conducted with double lines method respectively and under two kinds of densities. Variation of wetting strains (i.e., the differences between strains of dry and saturated states under the same vertical deviatoric stress) is analyzed. Results show that, there are two development stages of filler wetting strain curves. The positions of the change points of the two stages are closely related to the ratio of vertical deviatoric stress and confining pressure. Values of the wetting strain at change points on the curves of fillers with same density under different confining pressures are comparably consistent. They can become larger as the filler density increases. This indicates that the density and confining pressure have effects on both the magnitude and the rules of wetting deformation. Empirical formulas of wetting deformations and vertical deviatoric stress are put forward using the test results of three kinds of confining pressures. and the formulas are then verified with the test results of a new kind of confining pressures. These formulas can be applied to analyzing the laws of embankment wetting deformation in highway construction.