Wetting deformation of coarse grained soil is an important problem in earth dam design; but it is not solved well so far. The wetting deformation tests under various stress levels are carried out on a coarse grained soil; and the wetting deformations and curves of stress-axial strain-volume strain are obtained. The test results and analyses indicate that; the wetting deformation of the coarse grained soil is varied with cell pressure and wetting stress level; the ratio of wetting volume strain versus wetting axial strain is decreasing with the wetting stress level increasing; the wetted sample behaviour may be elacstic first elastoplastic after

while new load is forced on the sample; the method of single line for calculating wetting deformation is better than double lines. At the same time

a new method of improved double lines for calculating wetting deformation is proposed; the maximum wetting stress level is defined and used to explain the test results. The results may be significant to farther research on wetting deformation.