Abstract: In this paper, from the perspective of surface modification of filter material, how to improve its stability in high humidity environment has been studied. Using polyethylene terephthalate (PET) filter material as the substrate, ethyl orthosilicate (TEOS) as the precursor, and methyltriethoxysilane (MTES) as the low surface energy substance, the sol-gel method was used to generate in-situ on the surface of the filter material SiO₂ nanoparticles to prepare modified SiO₂ gel-coated filter material. Then, FESEM-EDS, FTIR and a contact angle measuring instrument were used to analyze the changes in the surface chemical composition, wettability and surface morphology of the PET filter material. The results show that SiO₂ nanoparticles are formed on the surface after finishing, and the surface is covered with hydrophobic methyl groups after MTES modification treatment. Thus, its hydrophobic property is significantly improved, and its surface water contact angle reaches 154.11°. At the same time, the SiO₂ particles are evenly distributed on the surface, and the gel polymer is only deposited at the intersection of the fibers, which ensures air permeability, and the filtration efficiency increases from 97.0595% to 99.2028%, and the filtration quality factor increases by 30%, from 0.02124 to 0.02761.