Abstract: To address the ubiquitous problems associated with silty clay in engineering applications, such as insufficient mechanical strength, poor durability and poor environmental adaptability, this study proposes a composite modification using guar gum (GG) and basalt fiber (BF) synergetic curing. Its multiscale action mechanism was revealed, and its enhancement effect was systematically evaluated. The mechanical properties and durability were systematically evaluated through unconfined compressive strength, wetting and drying cycles, infiltration, and water stability tests; the microscopic mechanism was revealed through a combination of X-ray diffraction (XRD) and scanning electron microscopy (SEM); and molecular dynamics simulation was used to analyze the interfacial adsorption and energetics characteristics. The results revealed that when 0.4% GG and 0.3% BF were added, the 60d compressive strength increased from 0.457 MPa to 4.25 MPa, and the effect of multiple blending was significantly greater than that of single blending. The permeability coefficient is reduced by a maximum of 85.9%. The mass loss rate after 10 wetting and drying cycles was only 6.5%. The compressive strength is 1.7 times greater than that of the cement-cured soil, indicating excellent water stability and durability. Microscopic analysis revealed that GG and BF improved particle bonding and structural compactness through gel encapsulation and fiber architecture rather than the formation of new crystalline phases. Molecular simulations reveal a hierarchical interfacial mechanism of “gel–fiber synergy”: long GG chains undergo physical entanglement on the BF surface and form multiple hydrogen bonds with Si-OH and Al-OH sites, with an interfacial binding energy as low as −9597.3 kcal/mol, indicating highly robust adhesion.The synergistic effect of GG and BF significantly improved the strength, impermeability and durability of the consolidated soil at the macroscopic level and achieved interface stabilization at the molecular level. These results provide a theoretical basis for the application of glue-rebar composite materials in soil reinforcement and sustainable engineering. Practical value.