Plasmid DNA，a common tool of genetic engineering containing the independent genetic structure of the replication,is widely used in basic research of molecular biology，genetically modified detection，medical diagnosis and gene therapy- Plasmid DNA conformations are generally divided into three types：supercoiled，open circle and linear.Crude plasmid DNA often mixes with three configurations，and the amount of protein，RNA，endotoxin with the host genome DNA.These impurities need to be further refined as they affect subsequent applications.The new applications of plasmid DNA,refined technologies and products based on chromatography system，and quality analysis of purified plasmid DNA is reviewed in this paper.Finally，the trends of technology of high purity plasmid DNA and analysis of refined product are presented.