The strong permeability， high porosity， and easy disintegration of granite residual soil cause serious erosion in the surface layer of the slope. Both biocementation and plant roots can be used for shallow slope protection. This study conducted single biocementing， single root， and joint combined reinforcement tests to investigate the effects of root content and the biocementing time on permeability， water retention， disintegration， and shear properties. Then， the hydraulic properties of granite residual soil reinforced by biocementation joint root systems were systematically analyzed. The results showed that single root reinforcement primarily improved the shear characteristics of granite residual soil， but also increased its permeability. Single biocementation significantly improved the permeability， water retention， disintegration， and shear properties of granite residual soil； however， too many cementing times may weaken its shear resistance properties. The incorporation of roots under co-reinforcement increased the permeability of granite residual soil， while substantially improving the disintegration and shear properties， which was more pronounced with higher root incorporation. The disintegration process of the specimens under joint reinforcement was mainly divided into three stages， and the improvement effect of cohesion was much higher than the internal friction angle. The combined reinforcement of biocementation and root exhibits a significant synergistic effect， with biocementation playing a critical role in enhancing the hydraulic properties of granite residual soil， while root systems assist in regulating water movement.