To explore the effects of water-retaining agent on root growth and root-reinforced soil mechanical properties, and provide a theoretical basis for promoting mine restoration, a water-retaining agent was added to the potting soil of Robinia pseudoacacia, and three treatments were: B1 (0%), B2 (0.3%) and B3 (0.5%), respectively. The effects of water retention agent addition on the stability of root-soil complex were investigated by comparing and analyzing soil nutrients, soil enzyme activity, root growth parameters, root tensile strength and root-soil complex shear strength, and the correlation between them. The results showed that: (1) Under the concentration gradients of 0.3% and 0.5 % water retention agents, the addition of water retention agents reduced the tensile strength of Robinia pseudoacacia roots; (2)There were different effects on root-reinforced soil shear strength with different water-retaining agent concentrations, under the treatment of 0.3% water-retaining agent concentration, the root-reinforced soil shear strength was significantly reduced, while under the treatment of 0.5% water-retaining agent concentration, the root-reinforced soil shear strength did not change significantly; (3)Tensile strength and shear strength were negatively correlated with cellulose and hemicellulose, and positively correlated with lignin. The root-reinforced soil shear strength was mainly affected by cohesion. In conclusion, at the concentration gradient of 0.3% and 0.5%, the addition of water retaining agent decreased the tensile properties of Robinia pseudoacacia roots, and the mechanical properties of roots were significantly related to the internal components of roots.