This invention belongs to the field of inorganic/organic nanocomposite materials technology, specifically relates to a nano-SiO2/boron phenol-formaldehyde resin nanocomposite material and its preparation method. The invention combines solution blending with ultrasonic assisted dispersion to ensure that nanoparticles are dispersed at the nanoscale in the composite material; the surface of nano-SiO2 is treated to form a good interface between nano-SiO2 and the matrix resin boron phenol-formaldehyde resin, which can fully exploit the advantages of nano-SiO2 and boron modified phenol-formaldehyde resin. The purpose of this invention is to prepare boron phenol-formaldehyde resin nanocomposite materials with different contents of nano-SiO2 through reasonable process control. By utilizing the rigidity, wear resistance, thermochemical stability of nano-SiO2, and the good mechanical properties, heat resistance, and ablation resistance of boron modified phenol-formaldehyde resin, The prepared nano-SiO2/boron phenol-formaldehyde resin nanocomposite can be widely used in many fields such as high-temperature brake friction materials, ablation-resistant materials, special structural materials, and heat-resistant materials.