[Objective] The soil erosion of topsoil in agricultural forestry production in Loess Plateau was researched in order to provide scientific basis for the selection and allocation of tree species in ecological restoration in this area and its similar areas.[Methods] The shear mechanical properties of topsoil under four different vegetation community types including poplar + Caragana korshinskii mixed forest, poplar pure forest, Pinus tabulaeformis evergreen coniferous forest and C. korshinskii shrub pure forest were studied, and the influence of soil moisture content on its mechanical properties was analyzed.[Results] In the range of 2.5%~12.5% of the water content of the test topsoil, the shear strength and adhesion of the surface soil were increased with the increase of soil moisture content in 4 different vegetation types and bare ground, indicating that the increase of soil moisture played a positive role in improving the anti-erodibility of soil surface in a certain range. The shear strength and adhesion values of topsoil under 4 different vegetation community types were significantly larger than those of bare land, which indicated that the soil and water conservation measures had improved surface soil structure, thus improving the anti-erodibility of the surface soil. There was no significant change in friction angle of surface soil with the increase of water content in the range of 2.5%~12.5%.[Conclusion] The shear strength and cohesion of the topsoil under the mixed forest of lime + poplar were the greatest among the four different vegetation community types, which also explained the superiority of mixed forest in forest and grass measures of soil and water conservation.