To study the effects of soil moisture content on the residual strength of root-soil composites and pure soil, the shear displacements of shear apparatus extend to 14mm. The results indicate that the residual strength of root-soil composites of two plants and pure soil increase at the beginning and then decrease, with increases of soil moisture content. When the residual strength reaches the maximum, the soil moisture content was about 10.77%.The residual strength of root-soil composites of Caragana microphylla Lam. and Artemisia sphaerocephala Krasch. are both higher than pure soil under four kinds of soil moisture content, the variation tendency of cohesive strength of two plants and pure soil are similar with residual strength. The internal fiction angle decreases when soil moisture content increases.