With the development of nano-technology in the field of polymer

researchers pay attention to the condensed state of single polymer chain. Single polymer chains were existed in micro-particles with nanometer scale

and geometric entanglements were not founded between polymer chains. This article reviews the progress of single polymer chain in recent years. The preparation methods of single polymer chain are introduced

such as atomizer spraying

freeze-drying

microemulsion polymerization

reverse precipitation and surface film spreading

meanwhile the characterization methods of single polymer chain and computer simulation technique for the conformation of polymer chains are reviewed; in the last section

the application of single polymer chain and unimolecular micelles in preparation of metal nano-particles are represented and the coming research fields of single polymer chain are prospected.