Packaging bag can be seen anywhere, we will get all kinds of packaging bag when we go shopping .Different packaging have different characteristics, it will influence humans health directly, so the production requirements of the food packaging bag is more strict ,especially for high temperature cooking packaging, because harmful substance of plastic packaging will distributed under the effect of high temperature, it endanger foods safety .Now, cooking bag are used widely in the world, so what is cooking bag ,how does the cooking bag be composed? Cooking bag is kind of composite plastic film that can be carried out a heat treatment, it can be taken as tin container as well as cooking plastic bag. Most of the packing bag is made of three layers composite material, Outer layer is a polyester film for reinforcing; middle layer is aluminum foil, which can prevent light, damp, gas effectively; the inner layer is made of polyolefin film, which can be directly contact with foods. The outer material of the cooking and packaging bag has good printing adaptability, and the tensile strength, rigidity, friction resistance and puncture resistance are good. BOPA thin film, BOPET film are frequenly used for outer layer of cooking bag. The middle layer of the cooking and packing bag is the main functional layer, which generally has good barrier property, and can prevent the invasion of the oxygen and the harmful microorganism. Cooking the packing of the application of different target, intermediate layer material choice also has bigger difference, opaque cooking packing bag selection and aluminum foil as intermediate layer, intermediate layer of transparent cooking bags can be combined with the outer layer is a layer of. Cooking the packing layer material is heat seal, good heat seal performance is required, can withstand high temperature sterilization, the contents of pollution, generally take the CPP film. CPP is divided into two types, the average CPP because of high molecular regularity, resulting in low crystallinity, low temperature resistance, poor impact resistance, the sealing temperature is also high. Copolymerization CPP increased the molecular chain segment of the degree of freedom, so that the crystallization of polypropylene greatly improved, its low temperature resistance, impact resistance, greatly improved heat resistance temperature.