In order to study the effects of different arrangement modes on shear strength of herbal root-soil composites, the difficulty that the same root amount or root number could not simultaneously satisfy different arrangement modes(square,quincunx and ring) was solved effectively.On this basis, by taking the soil and sedge family plants in the north side of north-south transition zone of china as the research object, the shear strength of herbal root-soil composites were researched. The strengthening effects of the herbal root-soil composites and the variation of shear strength index were analyzed by using laboratory test under the disturbance of different levels of root amount and arrangement modes. The results show that the shear strength and cohesion of root-soil composites increased with the root amount increasing under the same conditions. The friction angle of root-soil composites exhibits almost no variation with the root amount increasing under the same conditions. The shear strength of root-soil composites and the cohesion increased with the root diameter increasing.The friction angle of root-soil composites exhibits almost no variation with diameters increasing The arrangement modes of herbal root had little influence on the shear strength of root-soil composites when the normal stress was comparatively small.The influence on the shear strength of root-soil composites of the arrangement modes could not be ignored when the normal stress was comparatively big.Moreover, The bigger the area replacement ratio, the larger errors.The results also showed that it was considered that the square arrangement exerted an important influence on the cohesion and friction angle of root-soil composites when the area replacement ratio comparatively small.The influence on the cohesion and friction angle of root-soil composites were gradually stabilized with the increase of the area replacement ratio.