Abstract: Objective The mechanical and hydrological effects of vegetation root systems reinforcing slope soil offer an eco-friendly approach to slope protection, enhancing stability. However, the complexity arising from the interdisciplinary nature of this field means its mechanisms of action remain incompletely understood. Methods This paper provides a systematic review of the mechanisms and research progress concerning soil reinforcement by plant root systems on slopes. It delves into the regulatory mechanisms of root systems on soil moisture, the reinforcing and anchoring effects of root systems on soil masses, the applicability and limitations of composite soil-root biomechanical models (WWM, FBM, RBM), and the quantification of root parameters in composite soil-roots using probabilistic analysis methods, along with integrated hydro-mechanical effects. Results The stability of slopes can be significantly enhanced through the hydro-mechanical coupling effect of plant root systems, leading to substantial improvements in the matric suction and shear strength of vegetated slopes. Current mechanical models have limitations: the Water-Flow Model (WWM) tends to overestimate the reinforcement effect, the Fiber Bundle Model (FBM) does not account for lateral root contributions, and parameters for the Root Biomechanical Model (RBM) are challenging to obtain. Probabilistic analyses indicate that the spatial variability of root systems has a significant impact on stability assessments. Conclusions This study has preliminarily elucidated the mechanisms of soil stabilization by root systems. However, challenges remain concerning model applicability and parameter quantification in complex environments, limiting robust support for refined engineering applications. Future research should focus on model optimization, improved parameter acquisition, and enhanced interdisciplinary collaboration to advance the precise engineering application of plant root systems for slope stabilization.