Abstract: This study investigates the anti-seepage effect of a capillary barrier consisting of a layer of fine-grained soil underlying and a layer of coarse-grained soil on expansive soil slopes through the numerical model.The moisture stress in expansive soil is applied to the soil in the form of a temperature stress field using the initial strain method，and the numerical simulation of hygroscopic expansion of expansive soil slope is realized by numerical software.The criterion for determining slope stability is whether the equivalent plastic strain zone is completely penetrated or not.The numerical simulation results indicate that the capillary barrier cover layer forming a strong permeable layer can effectively prevent rainfall infiltration and achieve a good slope protection effect.Under the selected operating conditions in this article，the slope protection effect of the capillary barrier cover layer composed of 0.5 m fine-grained soil layer and 0.2 m coarse-grained soil layer is equivalent to that of 1.5 m cement modified soil.The capillary blocking ecological slope protection structure has a good slope protection effect on expansive soil slopes.The research results can provide a theoretical and designed basis for related expansive soil slope protection.