Abstract: It is important to determine the seepage field parameters of high earth-rock-fill dam using the observed seepage data during operation period. For Nuozhadu core rockfill dam, the training samples are produced for saturated seepage field which is calculated by the finite element program. The nonlinear relationship between seepage parameters and water heads is established using the SVM mapping. Then taking the error objective function as the fitness value of particle swarm optimization (PSO), the seepage parameters should be identified by PSO. Based on the one-dimension consolidation theory, the dissipation formulae for the excess pore water pressure in the core wall are derived, and they are used to correct the measured seepage pressure values in the core wall. The recorded osmotic pressure curves of osmometers, which are distributed in the maximum section, are used for this back analysis. The permeability coefficients of the dam materials are retrieved using the corrected measured seepage pressure values under steady state of seepage condition, i.e., the water level remains unchanged. Meanwhile, the parameters are verified by the unstable saturated-unsaturated seepage field while the water lever rises. The results show that the permeability coefficients are reasonable.