Abstract: Wetting deformation of water storage has always been a technical issue that restricts the long-term safety operation of high earth-rockfill dams. The wetting deformation tests have been commonly carried out for rockfill materials, but seldom for gravelly soil core wall materials, which is mainly because it is difficult to carry out experimental studies due to the current testing techniques of gravel soil materials. By setting sand cores in large-scale gravelly soil samples to increase the water inlet channel and shorten the wetting path, the technical difficulties such as the long time required for the wetting deformation tests on gravelly soil core materials and the insufficient saturation of samples can be solved. Then the large-scale triaxial wetting deformation tests on gravelly soil core materials can be conducted successfully. The wetting test results show that there is obvious wetting deformation phenomenon in gravelly soil core wall materials. The axial and volume wetting deformations are closely related to the confining pressure and stress level. The relationship between the wetting deformation and the stress level increases with the increasing stress level when the confining pressure is small, and decreases with the increasing stress level when the confining pressure is large. The relationship between the wetting deformation and the confining pressure basically shows the deformation tendency of increasing first and then decreasing. Compared with that of rockfill materials, the wetting deformation tendency of gravelly soil core materials is more complex.