Abstract: Poly(vinyl alcohol) (PVA)/CuSO4·5H2O membrane was prepared by solution casting. The structure and properties of the membrane were investigated by scanning electron microscope, thermogravimetric analysis，X-ray diffraction, mechanical testing, and gas permeability testing. After introducing Cu2+ ions into PVA, bonding between Cu2+ and PVA chains may be formed and therefore reduce the crystallinity of the membranes. The membrane possessed higher tensile strength and lower elongation at break compared with neat PVA membrane. The cross-linking of CuSO4·5H2O markedly improved the mechanical properties of the membrane. Under 75 % relative humidity，the addition of Cu2+ to PVA membranes resulted in dramatical improvement of CO2 permeability coefficient, while the O2 permeability coefficient almost did not change.

Key words: poly(vinyl alcohol), pentahydrate copper sulphate, membrane, cross-link, gas permeabitity