In recent years, with the improvement of people’s living standards, food has become increasingly diversified, hygienic, convenient and high-end, and composite film flexible packaging has gradually occupied an important position. Retort packaging bag–Commonly known as soft cans, as a kind of film-compliant flexible packaging, it is generally used for the storage of food at room temperature. It is often used in the packaging of meat, bean products and other foods.(100~135℃)Heat sterilization can be stored at room temperature. The retort-resistant packaging bag is easy to carry, ready-to-eat, hygienic and convenient, and can well maintain the flavor of the food, which is deeply loved by consumers. According to different sterilization processes and packaging materials, the shelf life of retort packaging bags ranges from half a year to two years.The retort-resistant packaging bag food is heat-sterilized after the food is packaged together with the packaging material. In order to achieve higher physical properties and good barrier properties, retort food packaging bags are made of a variety of substrates, commonly used materials arePA,PET,ALandCPP, the common structure has two layers of composite membrane(likeBOPA/CPP,PET/CPP), three-layer composite film(likePA/AL/CPP,PET/PA/CPP)and four-layer composite film(likePET/PA/AL/CPP). High-quality high-temperature cooking food packaging materials should meet the following conditions:① Good mechanical properties, high strength, softness, can adapt to the needs of various packaging machinery, bag making machines, heat sealing machines ;② Good heat resistance, in121Cooking at ℃ temperature40min, The packaging film and bag are stable in size, no deformation, no delamination, no cracking at the heat seal ;③It has a high barrier property, and the oxygen transmission rate is lower than that of750px3/m2 24h 23°C,RH50%, the water vapor transmission rate is less than5g/m2·24h·38℃·atm, RH90%;④Excellent food hygiene, does not contain harmful substances, will not produce harmful substances after high-temperature cooking, long-term contact with food, stable chemical properties, will not chemically react with various ingredients in food, form substances harmful to the human body ;⑤ Good product display, highly transparent, and the surface can be printed in color.