The mechanical characteristics of soil-rock mixed accumulation with dense and loose compacts before and after wetting under different confining pressures σ₃ are studied by a large-scale triaxial slaking test using the dual-line method. The effects of wetting on secant modulus E₅₀, critical state friction angle, peak state friction angle and the position of critical state line are analyzed. Test results show that the wetting effect can attenuate the secant modulus E₅₀, critical state friction angle and peak state friction angle. The changing trend of Isotropic compression line (ICL) and critical state line (CSL) of the mixed deposits of soil and rock before and after wetting are clarified. Based on the state-dependent constitutive model of cohesionless soil, the stress-strain relationship of the deposit before and after wetting was simulated. Compared with the test results, it is found that the model simulation result can reflect the change of the dilatancy character of the deposit before and after wetting.