To address the limitations of conventional sodium silicate coatings—high water solubility, poor adhesion, and single functionality, this study introduces a three-stage gradient strategy of “molecular bridging-micropore filling-functional coupling.” Using a sodium silicate solution as the base material, a sodium silicate-polyvinyl alcohol composite coating was prepared via organic–inorganic hybridization. Further, the modified coating was strengthened by introducing nano-SiO 2 modified with silane coupling agent KH550, thus constructing a high-performance water-based composite coating system. Results show that through the molecular regulation of KH550, spatial orientation of its organic and inorganic ends is achieved, effectively suppressing nano-SiO 2 agglomeration and establishing a molecular-level connection at the wood-coating interface; Nano-SiO 2 fill coating micropores, significantly increasing cross-linking density and mechanical properties; Through the synergistic effect of the Nano-SiO 2/PVA/2NH 2-PDMS composite system, a “rigid Si-O-Si and type siloxane” dual-network structure is constructed, addressing the shortcomings of traditional coatings being hard and brittle; The composite exhibits outstanding performance: enhanced mechanical properties (wear resistance: 0.083 g/r, hardness: 6H), adhesion meeting Grade 1 standard, essentially no residual contamination from cola, soy sauce, or sesame oil, and rapid, smokeless self-extinguishment. It fully meets application requirements in furniture, interior decoration, and construction, offering a new approach for high-value utilization of bio-based materials.