<p>To optimize the stress distribution of the face slab, high retaining walls have recently been constructed at the toe of concrete face rockfill dams. The stability of such retaining walls is critical for dam safety. However, an accurate quantitative method for calculating earth pressure on high retaining walls remains lacking. Based on the distinct stress states of the rockfill behind the high retaining wall, the backfill was divided into four zones, and the influence of each zone on the earth pressure was analyzed separately. A semi-analytical method was proposed based on Rankine’s earth pressure theory, incorporating two key parameters obtained through a surrogate model. This surrogate model, developed using the particle swarm optimization (PSO) algorithm and the Kriging model, demonstrated high predictive accuracy. The Coulomb’s active earth pressure theory was shown to be unsuitable for the exploration of earth pressure on high retaining walls in concrete face rockfill dams. The proposed semi-analytical method was validated through the numerical simulation of a dam in China, which indicated close agreement with the simulation results and a relative error of less than 10%. The key parameters required for the method were accurately derived from the PSO-Kriging surrogate model. This study confirmed the superiority of the proposed method in calculating earth pressure on high retaining walls in concrete face rockfill dams.</p>