Conjugated polyene bonds on poly(vinyl chloride) (PVC) films were rapidly formed by the treatment of oxygen plasma produced by microwave discharge. Changes affecting the formation of conjugated carbon bonds on PVC were studied with respect to plasma emission diagnostic and surface properties of the film with fluorescence, refractant absorption spectroscopy, X-ray photoelectron spectroscopy analysis, and Raman spectroscopy. The formation of polyene bonds on the film surface was responsible for both the dechlorination and dehydrogenation of PVC in the plasma atmosphere.