Poly(n-butylamino)-(di-n-hexylamino)-phosphazene was prepared by the reaction of poly(dichlorophosphazene), di-n-hexylamine and n-butylamine using tetrahydrofuran (THF) solvent and triethylamine at room temperature. To increase the mechanical properties of polymer films, cross-linking agents, such as neopentyl glycidyl diether and trimethylol propane triglycidyl diether, were added to the original polymer. The original and agent-added polymer films were prepared by a casting method. The films with cross-linking agents were heated at 60 and 120 degrees C, and then transparent films were prepared. The oxygen gas permeability and the mechanical properties of the original and the cross-linked films were determined. It was found that the oxygen gas permeability and the mechanical properties, such as Young’s modulus, of the cross-linked films were greater than for the original film.