With the increasing requirements for printing, packaging, sealing and protection, handling and storage of products, it is impossible for a single plastic to meet all of these requirements at the same time, so multi-layer materials are needed to combine their advantages. In film processing, a raw material is extruded onto another film that has been made or different types of films that have been made are adhered to each other to form a multilayer film. This product is called a composite film. The material of the composite film is mostly plastic, but paper, metal foil (usually aluminum), or fabric can also be used. The basic requirement of a composite film is to have good adhesion between layers to ensure the overall mechanical properties of the package. In addition, composite films are mostly used for food packaging. Adhesives are used in the processing of composite films. The selection of solvents and bonding processes must meet the requirements of corresponding sanitary standards. Coextruded film has most of the characteristics of composite film, but there is a difference, that is, all layers of coextruded film are extruded at the same time, so there will be no other non-plastic materials such as aluminum foil, paper. Its product materials have relatively few combined forms, and the scope of application is also small. However, since the winter fusion layer and the layer are bonded by hot melt without the need for an adhesive, the hygienic safety of the co-extruded film of food packaging is relatively reliable.