Abstract: Poly(trimethylvinyloxysilane) (Ⅰ) was synthesed by polymeric reaction of polyvinylalcohol with chlorotrimethlylsilane in DMF. The active thin composite membrane for oxygen enrichment was cast from the solution of (Ⅰ) onto a porous polypropylene support (Duragard 2400). crooss-sectionnal SEMs of the composite membrans showed that the thickness of the active thin layer was aboat 1μm. (Ⅰ) has excellent performance: permeability P_o2=1.18×10^-4cm³cm/cm²·sec·cmHg, separation factor of oxygen from nitrogen α_N2^θ2=2.93. The performance of oxygen enrichment changes slightly when the composite membranes was aged for three months at room temperature.