Abstract: As the coarse granular materials are widely used in dams and roadbeds with high requirements for deformation control, it is critical to study the wetting deformation of the coarse granular materials. By analyzing the existing research results, a torsional plane relationship is put forward among the mean principal stressp, the generalized shear stress q and the ratio of wetting volumetric strain to wetting axial straink. When k is constant, the torsional plane becomes a straight line through the origin in the p-q plane. Using the above findings, the formula for calculating k is deduced, which is in the form of logarithmic function of q/p. To illustrate its rationality and practicability, some triaxial wetting tests are numerically simulated using the proposed relationships. The results show that the law and the proposed method for calculating the wetting strain of coarse granular materials are reasonable and practical.