Abstract: Wetting deformation is part of the main post-completion deformation of earth-rock dam, which has important influence on the stress deformation behavior of dam body and the safety of dam body for initial impoundment. Based on the previous research results of wetting deformation characteristics, the proposed wetting deformation model, and further comprehensive analysis of a large number of wetting test results, this paper summarizes and improves the relationship between wetting strains and their variation rules, and deduces the elastic and plastic mechanical parameters representing this characteristic. Under the framework of nonlinear elasticity theory, a new formula for calculating Poisson's ratio of wetting is proposed, and the close relationship between the wetting Poisson's ratio, the average effective stress p and the generalized shear stress q is established. In the framework of plasticity theory, an accurate wetting dilatancy equation is presented. It is found that the correlation coefficient between the calculation results of the Poisson's ratio and dilatancy ratio proposed in this paper and the test data is above 0.95. Therefore, the calculation methods of the wetting Poisson ratio and the wetting dilatancy ratio proposed in this paper are generally applicable, accurate and reliable, and the research results can provide important reference and support for the study of the wetting deformation characteristics of rockfill and the elastic or plastic simulation of the wetting deformation of rockfill dams.