Low temperature rf-plasma was used to create a plasma-treated polymeric composite membrane made from CHF₃, a material that is very thermally and chemically stable. The chemical and physical properties of the CHF₃ plasma polymers were variously changed by plasma treatment on membrane surface. CHF₃ plasma polymers were efficiently deposited on an aluminum oxide substrate with a pore size of 0.02㎛ at the plasma polymerization time 60 min, the rf-power 160W, and the flow rate of the CHF₃ 16 sccm. It was found that O₂ plasma treatment had a much greater effect on the surface roughness of the CHF₃ plasma polymer than did Ar or N₂ plasma treatment. The attachment of functional groups to the CHF₃ plasma polymer surface as a result of plasma treatment increased the intensity of the oxygen functional group peak. It also increased the oxygen content and the O/C ratio. The plasma treatment also made to the surface that became to hydrophilic. The most effective hydrophilic surface modification occurred when the composite parameter raged from 300-450 kJ·s/kg. It was confirmed that the gas permeability and selectivity changed as a result of crosslinking, chemical etching, and the importing of functional groups to the CHF₃ plasma polymeric membrane.