Abstract: Nano-SiO₂ was prepared by sol-gel method. Then the silanization of nano-SiO₂ was carried out by adding silane coupling agent 1, 1, 3, 3-tetramethyldisiloxane and obtained a silanized nano-SiO₂ that was used to modify phenolic resins (PR1 -PR6). These modified phenolic resins were then converted into the corresponding phenolic foam (PF1 -PF6). FT-IR, TGA/FT-IR and TGA were applied to investigated the properties of these modified phenolic resins. The test results showed that the modified phenolic resin has successfully incorporated silanized nano-silica via the chemical crosslinking reaction that formed Si—O—Si and Si—O bonds. Free phenol test results showed that with the increase of nano-silica content, the free phenol content drastically decreased. However, the same content of tetraethoxysilane(TEOS) with the different content of silane coupling agent had little effect on the free phenol content. When the silicone grease was 3.22 g and the silane coupling agent was 2 g, PR4 composition had the best performance. It was also found that with the increase of nano-silica content, the hydroxymethyl content rapidly increased to a high value. The mechanical properties test showed that when the mass fraction of silicone grease was 0.5% (calculated by the mass of phenolic resin, the same below)and the silane coupling agent was 0.3%, the flexural strength and compressive strength of PF4 were increased by 73.3% and 83.4% respectively, while compared with those of PF1, which resulted in the improve of the mechanical properties of the foam. In view of these test results, PF4 has exhibited the best modification effect and met the initial requirements.