Plastic bags are generally made of polyethylene by blowing technology, can be divided into high-density polyethylene and low-density polyethylene two. The polyethylene plastic is heated, melted and plasticized to be blown into a film cylinder; secondly, a bag making machine or a heat sealing machine is used for cutting the barrel material into a hot synthetic plastic bag. Plastic bags can be divided into granulation, blow molding, printing, pressing bags and cutting bags of 4 processes.