A method of preparing hydrophobic porous silica includes reacting a porous silica particle containing a hydrophilic group in a solvent with an organosilane compound under a basic catalyst to form a mixture, drying the mixture comprising the porous silica particle in a vacuum, and condensation reacting the hydrophilic group of the porous silica particle with the organosilane compound on the surface of the porous silica particle to modify the surface of the porous silica particle to be hydrophobic.