A method for preparing permanently hydrophobic 
aerogel and permanently hydrophobic 
aerogel prepared by the method. The method comprises adding 
sodium silicate to HCl at 30 to 90° C. until an acidity reaches pH 3-5, to form silica hydrogel under acidic conditions of pH 3-5, washing the silica hydrogel with 
distilled water using a mixer, followed by filtering, adding the silica hydrogel to a silylating solution of silylating agent in n-
butanol at pH 1-5 using an acid selected from 
hydrochloric acid, 
sulfuric acid, 
phosphoric acid and 
nitric acid, to simultaneously conduct 
silylation and 
solvent replacement, and 
drying the silica hydrogel; The method has the following advantages; i) 
silylation and 
solvent replacement can be simultaneously conducted, ii) n-
butanol is used as a reaction 
solvent instead of 
methanol upon 
silylation, thus obtaining a 
thermal conductivity comparable to conventional 
aerogel powders, iii) silylation is conducted under improved conditions, i.e., strong acidic conditions of pH 1-5, and as a result, all of the aerogel powders can be reacted with a silylating agent, thereby obtaining permanently hydrophobic aerogel, iv) the washing with a mixer makes the amount of removed 
sodium ions uniform, thus it is suitable for 
mass-production, and v) the method provides a relatively simplified procedure and the use of the silylating agent in a small amount enables low costs and 
mass-production.