The super water-repellent composite membrane were obtained using "grafting-from" polymerization with azo initiator chemically bonded on porous silica surface and radical-chain polymerization of fluorinated monomer. The synthesis of the fluorinated polymer brushes, membrane characterization were measured by XPS(X-ray Photoelectron Spectroscopy), SEM(Scanning Electron Microscopy), contact angle measurement, and permeation test. A liquid droplet on the ultra-hydrophobic surface has a contact angle as large as 160 ℃ with apparent surface free energy of ca. 0.1 dyn/cm. The first application of the surface to 4th generation composite membrane is also describe. Permeability measurement was performing simple time-mass measurements using water and MeOH. The permeability of the membrane was changed remarkably by the surface modification with PFA brushes.