In this study, we used the direct shear apparatus to study the direct shear friction characteristics of root- soil interface under different soil moisture content in the Midwest of Inner Mongolia. Five kinds of typical local plant, including Caragana Korshinskii, Hippophae rhamnoides, Hedysarum fruticosum, Medicago sativa and Astragalus adsurgens, were selected as experiment plants. The results showed that friction coefficients of root-soil interface for the five plants were all higher than those of soil - soil interface when soil moisture content varied between 4.5% and 24.5%. And friction coefficients of root-soil interface and soil-soil interface both decreased with the increasing of soil moisture content. The friction coefficient of root-soil interface and cohesion of Hippophae rhamnoides were both greater than those of other four plants, and this indicated that the effect of Hippophae rhamnoides roots on soil erosion resistance was greater than the other four plants according to the interaction between root system and soil. The cohesions of root-soil interface and soil-soil interface all increased first and then decreased with the increasing of soil moisture content. For different plant species, the soil moisture content was different when the cohesion peak appeared.