The wetting of rockfill material can easily lead to the uncoordinated deformation between it and the core wall, thus causing longitudinal cracks at the top of the dam and endangering the safety of the dam. Through the large-scale triaxial compression test and triaxial wetting test of rockfill materials of a hydropower station, the relationship between dilatancy ratio and stress ratio during loading and wetting process, and the relationship between wetting strain and confining pressure and stress level were studied respectively. The results show that the peak strength of the wetting specimen is basically the same as that of the initial saturated specimen, that is, the stress level of the specimen during wetting has little effect on its peak strength, but the final volume change of the specimen is obviously affected by the stress level during wetting. Therefore, the calculation of the wetting deformation of the earth-rock dam should be based on the single-line test. The consolidation of confining pressure and stress level during the triaxial wetting test has a significant effect on the wetting strain value. The higher the confining pressure, the larger the wetting volume strain, the higher the wetting stress level, and the larger the axial wetting strain. Based on this, a wetting strain calculation model considering the influence of confining pressure and stress level is proposed. In the process of loading and wetting, rockfill materials obey different stress dilatancy equations. When constructing the elastoplastic model of wetting deformation, different plastic potential functions should be used to describe the loading strain direction and wetting strain direction of rockfill materials respectively. The research results have certain guiding significance and engineering application value for the simulation of wetting deformation and crack prediction of earth-rock dams.