A method and a product of one-time enveloping silicone gel with plastic films. The surfaces of two films to be in contact with the silicone gel are treated by a plasma casing process (crosslinking by activated species of inert gases) or an electron beam process in advance so as to improve the wetting capability thereof. Thereby the films and the silicone gel are able to tightly combine together without the fear of separation. The operation is carried out under a vacuum environment so that no bubble will be generated therein and the leakage of the silicone gel on welding portions will be prevented.