The invention relates to the technical field of coating films on the surface of a photopermeability element, and in particular to a structure and method of a film layer of a sterilization coating film. The structure includes a film layer main body which is arranged on the surface of a base body. The film layer main body includes at least one film layer unit which includes a film layer unit assembly layer A and a film layer unit assembly layer B which are successively laminated in the direction away from the surface of the base body. The film layer unit assembly layer A is made of silicon dioxide, and the film layer unit assembly B is made of silver chloride. According to the invention, the film layer main body has excellent sterilization and permeability-increasing properties.