Canned food is food packed in tin cans or glass cans. The preparation method of canned food is one of the preservation methods of food processing. Food or food raw materials that meet the requirements are put into containers, and are made by production processes such as exhaust, sealing and sterilization. The production process of canned food usually includes raw material sorting, seasoning, seasoning processing, canning, exhaust sealing, sterilization and cooling. If the food raw material is fluid, after conditioning, heating, sterilization and cooling, it is packed in a sterile room or filled with inert gas to achieve the purpose of isolating microbial pollution after sterilization. Although the operation process is different, it can also be included in the scope of canned food. Sealing is to prevent external microorganisms from invading the inside of cans, and heating sterilization is to kill internal microorganisms such as pathogenic bacteria, poisonous bacteria and spoilage bacteria. Therefore, canned food can be preserved for a long time without deterioration.