Fabricating advanced polymer composites with remarkable mechanical and thermal conductivity performances is desirable for developing advanced devices and equipment. In this study, a novel strategy to prepare anisotropic wood-based scaffolds with a naturally aligned microchannel structure from balsa wood is demonstrated. The wood microchannels were coated with polydopamine-surface-modified small graphene oxide (PGO) nanosheets via assembly. The highly aligned porous microstructures, with thin wood cell walls and large voids along the cellulose microchannels, allow polymers to enter, resulting in the fabrication of the wood-polymer nanocomposite. The tensile stiffness and strength of the resulting nanocomposite reach 8.10 GPa and 90.3 MPa with a toughness of 5.0 MJ m(-3). The thermal conductivity of the nanocomposite is improved significantly by coating a PGO layer onto the wood scaffolds. The nanocomposite exhibits not only ultrahigh thermal conductivity (in-plane about 5.5 W m(-1) K-1 and through-plane about 2.1 W m(-1) K-1) but also satisfactory electrical insulation (volume resistivity of about 10(15) Omega.cm). Therefore, the results provide a strategy to fabricate thermal management materials with excellent mechanical properties.