Abstract: In the process of rapid economic development in China, natural geological processes and human engineering activities produce a large number of slopes, which pose a great threat to people's lives and property. In order to solve this kind of disaster effectively, scholars at home and abroad have carried out a large number of researches on plant slope protection technology. Plant slope protection technology uses the close entanglement between plant roots and soil to improve the shear strength of slope soil and enhance the stability of shallow slope soil. This paper mainly summarizes the changes of shear strength of herbaceous plant and woody plant root soil composite from the aspects of root distribution, root diameter, root number, soil moisture content, dry density. In addition, it analyzes the differences between the shear strength characteristics of undisturbed soil and remolded soil, and briefly discusses the research status of theoretical mechanical model of plant reinforcement. Finally, some prospects for the research on shear strength of root-soil composites are put forward.