Objective The area of sloping farmland in central Yunnan accounts for 61.14% of the total arable land area, and its sustainability is affected by serious soil erosion. Thus, it is urgent to study the positive effects of the rational allocation of vegetation on the sloping land space on improving soil erosion and maintaining sustainable agricultural production. About 89.4% of the sloping farmland utilization in the province is for planting crops, and maize and soybean are the main crops in summer. Previous studies have shown that the soil-fixing capacity of vegetation roots plays a significant role in soil and water conservation. This study was conducted to explore the soil-fixing effect of corn and soybean roots and to provide a basis for the calculation of the soil-fixing ability of crop roots.Method In this study, a field experiment was designed to have three treatments and a total of 9 experimental plots; i.e. CK (Bare land), MM (mono-maize) and SS (mono-soybean). The unconfined compression tests were used to determine the shear strength and stress-strain characteristics of rootless soil and root-soil composites of maize (Zea mays L.) and soybean (Glycine max L.) at the mature stage. The WinRHIZO (Pro.2019) system was employed to analyze the root distribution and configuration characteristics. And then the relationship between shear strength and root parameters was studied.Result The results indicated that: (1) Compared with rootless soil, the roots of maize and soybean significantly enhance the shear strength of root-soil composite (P < 0.01), and the strength of the root-soil composites was increased by 117.65% and 71.91%, respectively; (2) The cohesion of two crop root-soil composites were significantly positively correlated with root length density, root surface area density, root volume density, and root weight density (P < 0.01). Also, the contribution of fine roots with D ≤ 1 mm to the cohesive force increment was greater than that of other diameter-level roots; (3) In the different root architecture traits, the number of root branches of maize was 45.44% higher than that of soybeans, and the root distribution of each diameter class was more even. The corn root-soil complex showed weak strain-hardening characteristics when the root content was increased. Also, the crack propagation slowed down and the lateral deformation decreased.Conclusion The root systems of the two crops could enhance the shear strength of the soil. However, the different root structure types demonstrated different effects on the mechanical properties of the soil. The maize root system with more fine roots and more branches can effectively enhance the strength and restrain the deformation. Thus, fibrous root maize is better than taproot soybeans in holding the surface soil. In the use of sloping farmland, it is possible to prevent soil erosion by rationally arranging fibrous root crops. This study provides a reference for the rational layout of crop planting to prevent soil erosion on slope farmland.