Super-fine glass fiber is a kind of inorganic fibers, which has small volume density, low thermal conductivity, better sound absorbing performance, corrosion resistance and stable chemical properties, etc. In this paper, glass fibers are prepared by the flame blow process. Phenolic resin is used as a binder to obtain excellent flame retardancy and hydrophobic performance. The structure, acoustic performance and hydrophobic performance of glass fiber felts are characterized by scanning electron microscope (SEM), optical microscope, thermal conductivity analyzer, standing wave tube and contact angle tester. The results show that the fiber diameter presents normal distribution,mainly concentrated in 2.2 μm; The contact angle of glass fiber felt is 142° and the hydrophobic property is 98.9%. With the increase of density of glass fiber felts, the thermal conductivity reduces along with the increase of sound insulation. The design of the layered structure and refinement of glass fiber can improve the heat preservation and the sound insulation performance of glass fiber felts.