In order to explore the influence of vegetation root content on the water holding and permeability characteristics of expansive soil, samples with different root content were prepared by mixing bermudagrass roots with expansive soil from Nanning expansive soil area, and indoor pressure plate test and variable head permeability test were conducted, the Van Genuchten-Mualem model was used to predict the unsaturated permeability coefficient of expansive soil with different root contents.. The results show that the water holding capacity of expansive soil decreases after the addition of roots, and the addition of roots increases the proportion of large and medium pores in the expansive soil. The higher the root content, the greater the proportion of large pore volume to total pore volume, and the greater the decrease in water holding capacity compared to pure soil; In saturated state, the permeability coefficient of expansive soil increases with the increase of root content; In unsaturated state, the permeability of expansive soil at low suction stage (0-25 kPa) increases with the increase of root content. As the matrix suction increases to high suction stage (200-1000 kPa), the effect of root dominant flow decreases, and the permeability of expansive soil with roots gradually tends to be lower than that of pure soil; The mesoscopic results indicate that the incorporation of root system causes through cracks in the expansive soil, which is a key factor affecting the water holding and permeability of the expansive soil. This study further reveals the mechanism and regularity of the infiltration enhancement effect of vegetation roots on expansive soil, providing a reference for comprehensive evaluation of the effect of vegetation protection on expansive soil slopes.