Polyethylene glycol (PEG) is a polymer which is widely used for covalent modification of biological polymers such as proteins and peptides. PEG is often used in drug delivery and drug modification technologies, which can be directly coupled to the drug, or attached to the drug surface and encapsulated in nanomaterials. A full understanding of the pharmacokinetic (PK) characteristics and biological analysis of PEG and PEG drugs is of great significance to evaluate their overall safety and promote the development of related technology. PEG antibody is an important tool to detect PEG-modified drugs, in PK studies and immunogenicity analysis.