The bilayer membrane which comprises a upperlayer of a medical grade polyurethane and a underlayer of a porous corsslinked network of gelatin and poly(vinyl alcohol ) was prepared. Possibilities of the membrane for the usuage as skin substitute were estimated by measuring tensile strength and elongation under dry or wet condition and biodegradation ratio, and also studied by permeabilities of water vapor and oxygen. The degree of swelling was decreased with increasing the concentration of closslinking agent. And the tensile strength was increased with increasing the concentration of crosslinking agent, from 500kg/cm² to 720kg/cm² at dry condition and from 150kg/cm² to 260kg/cm² at wet condition. The value of elongation was varied within the limits from 7% to 50% at dry condition and from 10% to 65% at wet condition. The rate of biodegradation was very fast at the initial state but it became slow down after 4∼6 days and accessed to the equilibrium state. Water vapor transmission rate and permeability coefficient of Of varied with the change of evaporating time of polyurethane membrane and their values were controlled 6∼1.8(mg/cm²/hr) and [10^-7∼10^-8cm^-73(STP )cm/cm²·sec·cmHg], respectively. Theas values of the bilayer membrane measured in this study were satisfied with those of ideal skin substitute.