The invention discloses a hydrophobic superfine glass fiber cotton felt. The felt is made of hydrophobic superfine glass fiber cotton and a hydrophobic phenolic resin adhesive, and glass fibers are prepared into superfine glass fibers with the fiber diameter of 1-2 microns by means of a flame method; meanwhile, in the process of producing the glass fibers, an atomization glue-spraying device is adopted to make the adhesive with a hydrophobic effect changed into mist, the mist is fully mixed with the flocculent glass fibers formed after the fibers go through high-speed high-temperature flame airflow so that each glass fiber monofilament can be evenly wrapped with a layer of the adhesive, the fibers are solidified and shaped after sedimentation, and finally the superfine glass fiber cotton felt which has the advantages of being small in fiber diameter, high in flexibility and air permeability, low in thermal conductivity coefficient, excellent in sound absorption and insulation performance and hydrophobic performance, long in service life and wide in application range is obtained.